Any To GIF - Convert any picture into an animated GIF file.
Wallpaper Engine - Wallpaper Engine enables you to use live wallpapers on your Windows desktop.
MotionGIF - An all-in-one, easy and feature-rich GIF animator for Web animation!
Lively Wallpaper - What is it? Lively is a Free and Open-Source Software (FOSS) for animated desktop wallpapers.
PicGIF - PicGIF for Mac is an intuitive and agile GIF maker that allows you to create animated GIFs from photos/videos on Mac OS X in a few seconds.
ScreenPlay - Open-source and cross-platform Wallpaper, Widgets and AppDrawer app.