Hmm, I happened onto this website ookaboo, "ookaboo: free pictures of everything on earth". at first, I thought it was just for schools, but I see this photo, of five living US presidents:
http://ookaboo.com/o/pictures/picture/3965826/President_George_Wwith this Legal Notice:
"Can I use this image for my creative project?
Yes!
This image is in the public domain and may be used for any purpose, commercial or not. We believe that you should give attribution to the photographer, but this is not required."
Which is the same notice as is on a random selection of other images on the site.
Someone is going to be in very big trouble one day, when someone uses that (or any of many others) image commercially, for 'any purpose'.
