I know it's an old technology, and perhaps not as impressive as FLASH or some of the other hi-tech scripts which are being used today, but I've always liked GIF files. I actually like their simplicity. I've made quite a collection of them over the years, and thought perhaps since there are so many threads here for people to share their customized desktops, some people might also like to share their custom GIFs.
Here is one of my favorites:
(You will need to click on the enlarge bar to see it animate)