I don´t think you can use gifs, but it´s possible to make animated wallpapers. Animated Wallpaper Maker from Desktoppaints can do that (www.desktoppaints.com). I haven´t tried their animated wallpaper maker program, but i use DP Animation Maker when i make dynamic Playstation 3 themes and it looks like both programs includes the same animation effects.
Currently the Man of Steel logo (opening soon)! For some reason I always had this weird rule to myself about no nudity as my background, since lots of people see my laptop if I take it somewhere. Very scantily clad, sure, but no pure nude.