You should be able to search by the filename and/or by the Alt text used to describe the image. I would start with the filename. If the filename is generic (e.g. 001.jpg), then it will be close to impossible to find, and this is a very good example for why your filenames should be more descriptive.

Hope this helps!

Hey Brett,

Try this recent post on Searcher Intent:

http://www.seomoz.org/ugc/searcher-intent-my-main-focus-when-it-comes-to-keyword-research

I would say arrange for how it makes sense for users/searchers and not necessarily for search engines at all. Look to the audience and you'll be on target IMO.

Hope this helps!