I wish that was the only thing it was missing! If I did this in, say, Flash or SVG from the start, I think I could make many more things visible on mouseover. The PNG tools are the closest at hand, though.
I also wish it was easy to search for a particular movie. I wanted to show a friend the interesting path of Little Miss Sunshine, but it took me a while and some mousing to find it again.
It's pretty decent for aimless browsing around for interesting patterns, though.