If you’ve ever been cautious about downloading images and using them for fear that they are not actually public domain, this may be a great free resource for you to try on your next hunt for free images. The owner of Yotophoto contacts all the sites indexed and gathers feedback to make sure they are positive so the chances of coming across one that isn’t public domain or free to use is minimalized.
Yotophoto has already indexed over 100,000 images that are licensed under Creative Commons, GNU FDL, are public domain, and other free images. It also provides an advanced search feature allowing you to narrow your search by both size and license.