deskscapes also uses videos for it by the way. it doesn't use that much cpu or memory though, makes no difference for me at least.
At least most of them are right? I thought even the free version came with some water effect that was rendered on the fly. That's sort of a buzzkill I guess... I've been experimenting using the screen saver as the background. The ribbons screen saver takes like 3% CPU usage for my OC e7200, so not bad at all.
That's the free Dream Aquarium screensaver set to the background. I love it!