Backfract is an animated wallpaper program for Unix with X windows. 
It fills your background window with a fractal image, then every 
15 minutes it will update the image by zooming in or out. As it 
zooms in, it uses a simple heuristic to try to stay with 
"interesting" scenes. 

WWW: http://www.igoweb.org/~wms/comp/backfract/