I've been customizing my mac desktops/themes since about 1994. It is my favorite time-killer--changing desktops, icons, and messing with themes. As soon as I was able to take desktop screen-captures (which I probably discovered late) I started saving them. I put them(about 18 years' worth) into a movie.
If you're interested in this kind of thing, you can see it here: http://www.youtube.com/watch?v=U2MOcGHCBQo