I have always been a sucker for pretty wallpaper, especially satellite images of Earth. I think I have been trying everything available, but always found myself uninstalling it after a couple of days, usually because these things are resource hogs.
But now I have finally found something with looks and runs like a charm: Desktop Earth 2.0. It is freeware wallpaper that includes satellite images from NASA with resolutions up to 2560x1280. It also has cloud overlays (updated from satellite images). It runs either as active desktop or as normal wallpaper. Check it out now!