One improvement I think you could make is to AJAX it up, and instead of the entire page reloading, query a script to just get a random photo and update it on the page. That way, you reduce queries to your site, as they dont have to reload images over and over, which I believe could cut down on bandwidth (not entirely sure how much caching would affect that).

Anyway, nice site. Good job! Shame the .com was taken, but nice name nonetheless.