You know what would be cool? Add context to the photos yourself to make them searchable. This can be done by auto-tagging all photos so if I have a large album, I would be able to search where there's "garden" in the picture or "eiffel tower" in the picture and it gets me those pics. Much like Google's image search.
Nice idea. Not sure yet if it's a killer feature, but as you said, would be definitely cool.
So how could I get started? I can sure tag the photos but how could I get the "auto-tagging" working? Album name is not enough, so you must be thinking of something I have no idea nor knowledge of yet :)
If you need pointers, I would be glad to help!