1) On my work PC (running Windows 7) you can set up the wallpaper to be a slide show, so that it changes every 10 seconds (or longer).

2) Animated Gifs can be separated into individual frames.

3) You can turn an animated gif into a slowly animated wallpaper.

Do you know of any good SFW high resolution Gifs that could be used for this? I've currently gone with http://www.nasa.gov/sites/default/files/thumbnails/image/dscovrepicmoontransitfull.gif but I'm sure there are more exciting options.

Additionally, gif's definitely pronounced with a hard g isn't it?