A site that may be of interest (or a source :)): http://www.burningwell.org/
"BurningWell is a repository for public domain (free for any use) images. You are free to download, copy and use the photos you find here for any purpose."
They're running Gallery 2. I wonder how it will scale. They make anyone submitting a photo with people in it also submit a model release.
cheers Brianna