I wanted to try out video wallpaper (like DreamScene on Windows 7). I had tried XWinWrap with Hardy but back then, I had problems running Compiz on an old PC and it did not look good at all. Now, I am trying it out on a new PC and Compiz works well on my onboard Intel GMA 3000 on Ubuntu 10.04 Lucid Lynx Alpha.
If you want to try this, you must have compiz enabled. You may also want to install mplayer and codecs for videos you want to use as desktop background.