Why not classify the photos under arbitrary "qualities". Location, weather, etc., would be examples of such qualities. Others might include the names of people present in the photo, architectural style, trivia, history, odors, film speed, camera type, whatever.

By making the possible qualities arbitrary, you can add new categories as you go along, perhaps categories you had not considered. Then you have the luxury of executing ranked searches, such as "Chemistry Building, Outdoors, 2002, Summer" with leading qualities carrying more weight in the search/sort.

Once you figure all that out, then you can put a beautiful front-end on the thing for web browsing.

And then I can copy it because you open sourced it! I have a ton of photos I need to organize in this way.

Like how that works? ;-)

Matt