The genius brainchild of Lawrence Lessig, it has created a common source of media that is largely available to the public for a number of uses. It created the first real alternative to copyright restricted access to media. 

Image by: Grégoire Lannoy.

Attribution: Attribution 2.0 Generic (CC BY 2.0)
Location: http://bit.ly/1KveA9C

This link takes you directly to the public domain photos available via flickr. Also, you can reach a number of free flickr photos via Creative Commons.

Image by: Dimitar Nikolov.

Attribution: 2.0 Generic (CC BY 2.0)

Location: https://www.flickr.com/photos/dimnikolov/4076765969/

Wikipedia: "Instagram is an online mobile photo-sharing, video-sharing, social networking service that enables its users to take pictures and videos, and share them on a variety of social networking platforms..." Instagram's legal restrictions are a bit complex. Read before using.

Generally good quality, historical, sometimes retro, black and white.

Generally good quality, historical, sometimes retro, black and white.

Painting title: The Cestello Annunciation

Painter: Bottocelli

Attribution: "You are free to use up to five or six images from the site for any personal non-profit, educational purpose. This would primarily be your personal home page, but could also be, for example, one-time use for an offline presentation." Mark Harden Artchive. Read more.  

Location: http://www.artchive.com/artchive/b/botticelli/cestello.jpg

"On April 3, 2012, Google announced a major expansion to the Art Project as it signed partnership agreements with 151 museums from 40 countries" (Wikipedia). It is not at all clear what you can do with these images. As near as I can tell, you need to follow them back to their original source to see if you can download them for use. But, this gallery is so extensive, it is worth the work to do.

Photo title: screenshot taken and posted by Wikipedia, from the Google Art Project site of Manet's In the Conservatory

Location: https://en.wikipedia.org/wiki/Google_Art_Project

Amazing collection of historical posters. Permission to use the photos is vague in places, but it appears they can be used for non-profit purposes. As always, verify use on a case by case basis.

Poster title: "Lest we forget." Buy peace bonds. 1914-1918?

Artist: Unknown

Attribution: Unspecific. Read more.

Location: http://hvr.co/1RAkmZB

You can search the photo archives of the Library of Congress for weeks and just scratch the surface. Fortunately, the LofC provides good searching capabilities, and photos are grouped in collections. The collections contain what you would expect: US and world history told through photos, and much more.

Photo title: Old woman living in one of the slum "villages" in the northwestern part of the island. St. Croix, Virgin Islands

Photographer: Jack Delano

Attribution: "Transmission or reproduction of protected items beyond what is allowed by fair use or other exemptions requires written permission from the copyright holder." Read more.

Location: http://www.loc.gov/pictures/item/fsa1998010019/PP/

"The National Archives and Records Administration (NARA) is the nation's record keeper." NARA provides access to many historical images, videos, documents. Feel free to use them. Tax dollars paid for them.

Creator: Franklin Delano Roosevelt (my note: that is what NARA specifies)

Caption: "Facts the younger generation of marketers should know are taught this class in the Murch Elementary School, Washington, D.C. Catherine M. Rooney, 6th grade teacher instructs her alert pupils on the way and how of War Ration Book Two."

Attribution: Access/Use Unrestricted

Location: https://catalog.archives.gov/id/196400

The National Gallery of Art offers a number of downloadable images which they label "open access," which they define as follows: "Users do not need to contact the Gallery for authorization to use these images." NGA's collection offers images of paintings by some of the greatest artists of all time.

Painting by: Mary Cassatt

Title: The Loge (1882)

Location: http://1.usa.gov/1YwyQz2

Great repository of historical photos. Many are free to use. "Spanning a wide range of historical eras, geography, and media, NYPL Digital Collections offers drawings, illuminated manuscripts, maps, photographs, posters, prints, rare illustrated books, videos, audio, and more. Encompassing the subject strengths of the vast collections of The Library... represent(ing) the applied sciences, fine and decorative arts, history, performing arts, social sciences."

Sculptor: Bartholdi, Frédéric Auguste (1834-1904)

Citation: No known US copyright restrictions; other rights restrictions may apply

Location: http://on.nypl.org/1R22OFB

This presentation of free photo and image sites consists of links and wording from the following articles:

1. 14 Amazingly Free Stock Photo Websites, by Casey Ark, Contributor, CEO of Plato Web Design, published 10/20/2014 

2. The 8 Secret Places to Find the Best Stock Images, by Michelle Blackshire, Brand and Marketing Designer at Visually on 9/5/2014

3. 12 best places to get free images for your site, by Mike Williams, published 8/12/2009

4. 12 More Unique Places to Download Free Photos, by Liam Mckay, published 4/2/2015

5. 17 Amazing Sites With Breathtaking Free Stock Photos by Christopher Gimmer, published August 27, 2015.

I have identified each author (in parentheses). I left their text intact, except for the addition of a few comments. Keep in mind that many of these articles are not recent, and the sites they describe may have changed.

I don't include every site I find. If I elect not to list a site it is usually due to the site's lack of quality, or the site asks for too much personal information in order to use its services, or the site is too hard to navigate, or it is too difficult to tell whether photos really are free or not.

Do read the fine print, especially concerning commercial vs. non-commercial use. But these sites are included here because at the time I posted them, they had substantial holdings, parts or all of which were free to users. Things change, however. So be vigilant

This site tends to have more close-up images of animals, nature, people with a mixture of modern and vintage styles. Instead of a Tumblr-like user experience, you search by album and get a full collection of images for each subject. Currently there are about 30 albums, and with titles like Converse, Babies, Elephants, and Redheads, ...there is a fun range of topics for a variety of projects.  (Blackshire)

Photo title: Untitled

Photo by: Diane Metzler

Attribution:CC Noncommercial, no derivatives

Location: http://bit.ly/1Qv2sH6

One of the most exhaustive directories of open-source, it's my go-to resource when working on new web projects. While most stock-photo sites focus on a small niche (usually landscape photography), FreeImages offers thousands of pictures from  diverse categories. Most important, it's searchable...an incredible time-saver when working on a project. (Ark)

Searchable? Yes / Attribution required? Sometimes 

Photo title: By night : Charleroi, Belgium

Photo by: Thomas Boulvin

Attribution: FreeImages.com Content License License

Location: http://bit.ly/1Nsgz2m 

You can browse the tiny library at Free Media Goo in just a few minutes, and the images are relatively low resolution. There are some undeniably impressive photos, though, along with some handy textures and audio samples, and there's no need to register - just download anything that appeals. (Williams)

Photo title: Shattered diamon

Photo by: not specified

Attribution: This content is available for both commercial and private use free of charge. Read more. 

Location: http://bit.ly/1iL8DN5

Free Photos Bank

The Free Photos Bank site provides a typical range of free photos - people, animals, landscapes and so on. They're better at abstract shots, though, backgrounds and digital artwork, so this is a good place to start looking for those more unusual images. There's no registration required so downloading is easy, whatever you're after. (Williams)

Photo title: System Admin

Photo by: freephotosbank

Attribution: "Any photos/pictures posted by the author “freephotosbank” are free to use as long as you are using them for a website, book, magazine, etc." Read more.

Location: http://www.freephotosbank.com/182.html

The Freerange site search has an annoying habit of returning photos that have nothing to do with your keywords. But keep trying, and whether you're looking for animals or objects, people, places or arty, near abstract shots, you'll find a suitable high resolution shot here. (Williams)

Photo title: Going Social Concept - Networks Idea with Lightbulb

Photo by: Jack Moreh

Attribution: "When possible, please include a photo credit." Read more.

Location: http://bit.ly/1V8yOhq

If you need architectural or landscape photos fast, GetRefe is ideal. There are no frills, no categories on this site, just beautiful, natural images taken by a series of photographers traveling throughout Europe. (Ark)

Searchable? No 
Attribution required? No  

Photo title; Sea in a phone

Photo by: Refe

Attribution: Refe calls this "free." I am reading through the fine print.

Location: http://getrefe.com/downloads/sea-in-a-phone/

Gratisography's collection is, in a word, incredible. Built by the talented Ryan McGuire, an artist and web designer, this site features some of the most evocative images on the web and they requires no attribution whatsoever. (Ark)

Searchable? No 
Attribution required? No

Attribution: Not provided

Location: http://www.gratisography.com/#whimsical

IM Creator, which also offers an online website building tool, put together this small library of premium-quality free photos. Attribution is required but it's well worth it: These pictures are of the same, if not better, quality as those of paid sites. Photo by Instant Vantage. (Ark)

Searchable? Yes 
Attribution required? Yes 

Image by: Thomas Leuthard

Attribution: Attribution-ShareAlike 2.0 Generic (CC BY-SA 2.0)

Location: https://www.flickr.com/photos/thomasleuthard/8597609828/sizes/z/

Image*After didn't impress us with its conventional photos, but the more abstract efforts - everything from electronic components to brick walls and artistic blurs - are much more compelling, especially if you're looking for an unusual background image. (Williams)

Photo title: Dario Ice Sculptures

Photo by: not specified

Attribution: "You CAN use our images and textures in your own work, whether it be for personal or commercial use." Read more. 

Location: http://www.imageafter.com/image.php?image=b21dario169.jpg

One of Southern California's finest designers, Jay Mantri offers this eponymous collection, Jay Mantri, with free, inspiring photos that's updated every Thursday. (Ark)

Searchable? No 
Attribution required? No  

Photo title: Baby elephant

Photo by: Jay Mantri

Attribution: CC0 1.0 Universal (CC0 1.0) Public Domain Dedication

Location: http://s169923.gridserver.com/images/babyelephant.jpg

LibreShot reached out to me and made me aware of their site. It’s a fantastic collection of free photos that’s still growing. Attribution is required, so make sure you give credit if you use a shot, but other than that you’re free to do whatever you like with the photos. (McKay)

Photo title: Brown eye

Photo by: LibreShot.com

Attribution: Public Domain License (CC0)LibreShot

Location: http://libreshot.com/brown-eye/

This website was created by an advertising agency in Montreal called LEEROY Creative Agency. All images are free for any personal or commercial use. With multiple themes throughout each page, you’ll find a lot of great nature close-ups  including heads of lettuce, bees collecting pollen, even a polar bear under water. I find these images very useful for backgrounds and patterns. (Blackshire)

Photo title: untitled

Photoe by: Jordan McKeen

Attribution: CC0 1.0 Universal (CC0 1.0) 

Location: http://www.lifeofpix.com/?s=iphone

LittleVisuals is a unique site, run according to more of small-scale, handpicked approach than most stock-photo sites. (Ark) My note: Unfortunately, the site's creator passed away. We shall miss his work.

Searchable? No 
Attribution required? No  

Photo title: White church

Photo by: Nic

Attribution: None required

Location: http://littlevisuals.co/page/3

Lock & Stock Photos are the works of AJ Montpetit. He’s giving back to the open source community by sharing his photographs under Creative CommonsAttribution-ShareALike. (Gimmer)

Photo title: Don't Mess with Emu

Photo by: Lock and stock

Attribution: Let’s keep that great teaching of “Sharing is Caring” alive! I’m releasing these photos under the Creative Commons 0. More info.

Location: http://i2.wp.com/lockandstockphotos.com/wp-content/uploads/2015/07/IMG_4015.jpg

One of the simplest sites on this list, MorgueFile has a streamlined layout and carefully curated list of photos. Its selection isn't as large as some of the other sites on this list, but the photos included cover a wide range of topics. You can find images of everything from wildlife to antiques. (Ark)

Searchable? No  / Attribution required? No

Photo title: hand and light.JPG

Photo by: Jamierodriguez37

Attribution: You are allowed to copy, distribute, transmit the work and to adapt the work. Attribution is not required. You are prohibited from using this work in a stand alone manner.

Location: http://mrg.bz/MMY0ym

Negative Space provides 20 new photos every week released under Creative Commons CC0. The photos are searchable and can be sorted by category, copy space and color. (Gimmer)

Photo title: London map

Photo by: negative space

Attribution: All the photos and raw files on this website are distributed under theCC0 creative commons license. Read more.

Location: http://negativespace.co/photos/london-map/

New Old Stock is a collection of antique photos, many taken by government agencies or discovered in estate sales. You can scroll for hours without growing bored. (Ark)

Searchable? No 
Attribution required? No  

Photo title: Robot Arm Over Earth with Sunburst

Photo by: Unknown

Attribution: No known copyright restrictions

Location: https://www.flickr.com/photos/nasacommons/9461093248/

It first appeared back in 1998, and so it's no surprise that Openphoto has now built up a solid collection of stock photos. They're neatly arranged into well-chosen categories, and clicking any of these leads on to a thumbnail gallery of related shots. (Williams)

Photo title: untitled

Photo by: Sarah Klockars-Clauser

Attribution: Attribution 3.0 Unported (CC BY 3.0)

Location: http://openphoto.net/gallery/image/view/22455

It would take weeks to roam all the collections that this site links to. I got lost in the Oscars photos. "The stock images, film and photo archives listed provide a creative source for television producers, advertising agencies, libraries, education centres, picture researchers and Photojournalist researching visual communications." Usage rights vary.

Photo title: Keep your Beauty on Duty!

Photographer: Proctor and Gamble, appearing in Women's Home Companion.

Attribution: "...for use in research, teaching, and private study. For these purposes under Fair Use, you may reproduce (print, make photocopies, or download) materials from this web site without prior permission..." Read more. 

Location: http://library.duke.edu/digitalcollections/adaccess_BH0904/

The simplest site on this list, Picography is a scroll-through gallery of random shots offered by a handful of professional photographers. You can't search it but this site is perfect for designers looking for evocative photos. (Ark)

Searchable? No  / Attribution required? No  

Photo title: ART ALLEY RUN

Photo by: Kyle Kranz

Attribution: Creative Commons Public Domain CC0 licence.

Location: http://picography.co/photos/art-alley-run/

Picjumbo is a personal favorite of mine due to its easy navigation and extremely high-resolution photos (with no attribution required). This site also happens to sport a great collection of food shots, so if you're running a restaurant or nutrition-themed startup, you might find it worth your while to take a browse. (Ark)

Searchable? Yes  / Attribution required? No, for most images  

Photo by Viktor Hanacek

Attribution: "totally fee photos for your commercial & persona works"

Picjumbo

Picjumbo is a personal favorite of mine due to its easy navigation and extremely high-resolution photos (with no attribution required). This site also happens to sport a great collection of food shots, so if you're running a restaurant or nutrition-themed startup, you might find it worth your while to take a browse. (Ark)

Searchable? Yes  / Attribution required? No, for most images  

Photo by Viktor Hanacek

Attribution: "totally fee photos for your commercial & persona works"

Location: https://picjumbo.com/fresh-baguette-morning-breakfast/

Pixabay is a web designer's dream. Not only does this site offer an easy-to-use search feature, the images are absolutely brilliant. And most don't require any attribution at all. (Ark)

Searchable? Yes  /
Attribution required? No, for most images 

Photo provided by ShutterStock.

Attribution: CC0 1.0 Universal (CC0 1.0) Public Domain Dedication

Location: http://bit.ly/1G1Ekvu    

PLiXS was founded 2015 and has made it his goal to be the address in network for free and high resolution pictures and vectors. The information published on PLiXS images linked with the Public Domain CC0 license, which means that all the images may be used for private and for commercial purposes - for free and without naming opportunities.

Photo name: Old Book

Photo by: Tookapic

Attribution: Public Domain CC0 1.0. Read more.

Location: https://plixs.com/images/old-book-10951.html

Eclectic vintage pictures join ubermodern scenes at Public Domain Archive, an expansive online collection of images, many with striking symmetry and muted colors. (Ark)

Searchable? No  / Attribution required? No 

Photo title: TruDim Dimmable CFL R40

Photo by: bowmanlamps.com

Attribution:

Location: http://publicdomainarchive.com/

RareHistoricalPhotos.com is a website/blog exclusively dedicated to historical and rare photographs. Each historical photograph has a story to tell, each of them documents a major event in human history, each photo is a way to grasp the full meaning of the past.

Photo title: Testing football helmets, 1912 (flipped horizontal)

Photo by: Rare Historical photos

Attribution: "Most of the photos are copyright free / expired, but some of them are under the copyright law. It's better to do a thoroughly research in order on to have any legal problem. As for us, feel free to use the images as long as you credit the source. Good luck with your interesting project!"

Location: http://rarehistoricalphotos.com/testing-football-helmets-1912/

Get 7 free photos every 7 days. Photos are public domain and free from copyright restrictions. (Gimmer)

Photo title: not provided

Photo by: Monica Ricci

Attribution: free under CC0 1.0 

Location: http://bit.ly/1N2I93a

Splitshire is a collection of delicious free stock photos by web deisgner Daniel Nanescu. The photos are free for personal and commercial use. (Gimmer)

Photo title: Math on Walls

Photo by: Daniel Manescu

Attribution: To the extent possible under law, Daniel Nanescu has waived all copyright and related or neighboring rights to SplitShire Photos. This work is published from:Italia.

Location: http://www.splitshire.com/math-on-walls/

This website is a newer source for free stock images, with a library of pictures starting from May of this year. Created by Sculpt, the website features a lot of images of people working in coffee shops, along with the requisite mobile phones and laptops. It’s perfect for websites that regularly cover the free-lance or startup lifestyle. (Blackshire)

Photo title: untitled

Photo by: Startup Stock Photos

Attribution: CC0 — “No Rights Reserved”

Location: http://bit.ly/1KwN4Fv

StockSnap.io has a large selection of beautiful free stock photos and high resolution images. The site also has a very handy search feature making it easy to browse through the thousands of images available. In addition, the site tracks views and downloads so you can find the most popular photos available. StockSnap adds hundreds of images on a weekly basis and all photos are released under creative commons public domain – no attribution required. (Gimmer)

Photo title: not provided

Photo by: AJ Montpetit

Attribution: CC0 License. All photos on StockSnap fall under the Creative Commons CC0 license. Read more.

Location: https://stocksnap.io/photo/TCSL0ZGIT

Stockvault has a small but very high quality collection of stock photos, as well as logo templates, clip arts, textures and backgrounds. It's the perfect site to find graphics for your website, then, but beware - Stockvault's images are free for personal, non-commercial use only. (Williams)

Photo title: Me on the tire of haul truck

Photo by: Jochanan Wahjudi

Attribution: "We hereby grant to You a non-exclusive, non-transferable license to use the Image on the terms and conditions explained in this Agreement. FREE OF CHARGE." Read more.  

Location: http://bit.ly/1VIJvb5   

Streetwill.co provide free photos to use any way you want. As you can see from the examples below, the quality of these photos are top-notch and there’s a large number of photos to choose from. Be sure to Follow StreetWill on Twitter too and never miss any new photos. (McKay)

Photo title: Milky Way

Photo by: Banky Patchara

Attribution: CC0 1.0 Universal (CC0 1.0) 

Location: http://streetwill.co/posts/353-milky-way

Dutch artist Folkert Gorter and his graphic-design peers at SuperFamous curate this collection of incredibly high-resolution images, perfect for use in website design or as desktop backgrounds. (Ark)

Searchable? No  / Attribution required? Yes

Photo title: Dragonfly

Photo by: Michalel Hull

Attribution: Superfamous Images available under the conditions of a Creative Commons Attribution 3.0 license. 

Location: http://images.superfamous.com/Dragonfly

Tookapic stock is a marketplace for both free & premium stock photos. You can filter by free photos which are all released under Creative Commons CC0. (Gimmer)

Photo title: Bionicle robot

Photo by: Krzysztof Krupa

Attribution: Complicated, but you can filter for free photos. Read more. 

Location: https://stock.tookapic.com/photos/19999

This site has some great photos, with no significant restrictions on their use. You don't have to register to download images, and Unprofound is strictly non-profit, so you won't be hassled by the usual collection of annoying ads. What's not to like? (Williams)

Photo title: TN freak on the phone

Photo by: Jim

Attribution: "...you are free to use these photos for your CD art - personal or commercial." Read more. 

Location: http://bit.ly/1QcZqHA 

Unsplash adds 10 new royalty-free photos every 10 days and they're almost always of breathtakingly attractive beautiful landscapes. Just scroll down the home page to see foggy rivers, faraway mountain ranges or even battered signs in all their high-resolution glory. (Ark)

Searchable? No / Attribution required? Yes

Image by: Skyler Smith

Attribution: "Free (do whatever you want) high-resolution photos.

Location: http://bit.ly/1QSgF1u

A vast collection of the kinds of vintage photos that you can browse for hours. 

Photo title: Unspecified

Photographer: Unspecified

Attribution: "These are for you to use in your artwork and not for commercial reproduction in collage sheets etc. Most of these images are contributed by art-e-zine visitors and a big thank you to them."

Location: http://www.art-e-zine.co.uk/kooicollection03.jpg

From "14 Amazingly Free Stock Photo Websites" by Casey Ark: 

When you do a Google Images search, the resulting photos are not necessarily ones that you're free to immediately use. In most cases, the photos are still covered by photographers' copyrights.

If you're looking for photos to use for a design and want to keep yourself out of copyright trouble, you need to locate websites that explicitly define the copyright license of each image. For all the sites listed above, the license is generally pretty easy to find. There's typically a description of the license on every page or at least a link to a description. Here are two license types you're likely to find on these sites:

Creative Commons zero means that you can use the photos in any way you'd like, without asking permission.

Creative Commons with attribution means that you can use the photo in any way you want, as long as you credit the creator of the photo.

Attribution is simple: If you include a photo on one of a web page, add text that cites the photographer ("Photo by John Smith") and be sure to include a link to his or her site, if there's one.

Be sure to check each website's license page for specific details.

A version of this article first appeared on PlatoWebDesign.com.

Related: The 8 Secret Places to Find the Best Stock Images

My note: Try using the Copyright Advisory Network, maintained by The American Library Associations Office of Technology Policy, for practical apps that can help you determine copyright issues associated with using other people's work.

Compendia maintained by others

1. Incredible art department. Features links to many, many free or affordable image and art repositories.

2. 12 More Unique Places to Download Free Photos

Other sites

Unsorted for now. I have collected these over the years. In some cases, I am not sure whether they fit or not:

1. Free Graphics

2. Animation station

3. Background City

4. Getty Images - apparently, while you are free to use these images for non-commercial purposes, you can only do so by embedding the code they provide into your site. That is, you can't download the images and then simply add them using a standard editor. You need to use HTML.

5. Open Getty. Most content is historical, art and artifact related. "The Getty makes available, without charge, all available digital images to which the Getty holds the rights or that are in the public domain to be used for any purpose. No permission is required. All of the images can be found on Getty Search Gateway, and the J. Paul Getty Museum images can also be accessed on the Museum's Collection webpages." Many search results are not open for use. You need to look for the word download, and search with open content only filter turned on. I find their process very cumbersome, but they have some good materials.

6. Photo Collections. 

7. Rare Historical Photos. Fabulous photos with fabulous stories. I can't tell whether they can be used. Some are over 70 years old so should fall into the public domain. As of 10/8/2015 I have written curators of the site and have not heard back.