Public Domain and Royalty-Free Photographic Images
Pixabay.com
Pixabay has over 1.3 million images and videos. All contents are released under Creative Commons CC0, which makes them safe to use without asking for permission or giving credit to the artist – even for commercial purposes.
Photogen
Morgue File
Photo Rack
Free Images
The licensing terms for this site require attribution where technically possible. The images on this site are not licensed for use in products for resale.
Wikimedia Commons
https://commons.wikimedia.org/wiki/Category:Images
Stock Free Images
These images may have some restrictions and require attribution. Make sure that you read and understand the Terms of Use. An enhanced pprofessional plan is available.
http://www.stockfreeimages.com/
Photo Pin
These images are licensed under various forms of the Creative Commons license. Most require at least attribution. Make sure you read and understand the licensing terms on the site.
Pexels
Stock Photos For Free
http://www.stockphotosforfree.com/
Pond 5 Public Domain Project
Pond 5 is a major supplier of media clips and a good place to sell your own stock footage, images, music and sound effects. But, in addition to the media they have for sale, they have established a section of public domain media that is available for download at no cost. You’ll have to set up a free account to download the clips, but it’s worth the effort. Most of the clips and stills appear to be European and there are a lot of WWII vintage items.