LinPHA is an easy to use, multilingual, flexible photo/image archive/album/gallery written in PHP. It uses a SQL database to store information about your pictures. It comes with a HTML based installer, so you don't need experience in setting up SQL
NGPOD Wallpaper Changer is a program that is fairly self-explanatory from the title. Every day, NGPODWC accesses NGPOD’s(http://lava.nationalgeographic.com/pod/) database and shows a picture and description as a desktop wallpaper.