Keep coming up with interesting things like this and you'll find your calling (or land you an even better job than you're in now, if you're not in the biz.)
Great concept anyway. I think it you clean it up a bit, speed it up, add an admin section, etc it might be worth selling as a shareware web application (or even donateware... you'd be surprised). People pay money now for a program like slideshowpro which is flash-based. Again, not enough to pay the rent but a little extra $$$ on the side wouldn't be bad right?
Couple things to consider: I wouldn't load the full images right away... only the ones at the current zoom level. You could continue loading the other sizes in the background. If a user resizes on the fly then replace those low-res ones with the high-res when they load in. Some will be loaded, others won't be. It's a compromise. Might be worth playing around if you have extra time sometime.