On Thu, Jul 28, 2011 at 12:25 PM, David Gerard <dgerard@gmail.com> wrote:

There are open-source "similar picture" matchers. Running them over
the entire image archive might be an, ah, interesting experience.

Open source or not, TinEye and Google's "search by image" work just fine.

http://tineye.com/

http://www.google.com/insidesearch/searchbyimage.html