A highly customizable and easy to use wallpaper changer and manager. It will automatically change your background wallpaper depending on a wide variety of options, and is great for indexing large collections.

Main Features:
-Store multiple wallpaper lists in separate categories.
-The ability to rate wallpaper, so better ones are chosen more often.
-Minimises to tray area for easy access.
-Scan whole directories or drives for wallpaper files.
-Drag & drop files or directories to easily add wallpaper.
-Auto change the wallpaper when windows starts, every x minutes, or use ratings to choose an interval.
-Change wallpaper in order, in shuffle mode, or change randomly according to rating.
-Wallpaper can automatically be tiled ,centered or resized to full screen.
-Supports jpg and bmp formats.
-Simple but powerful interface.
-Wallpaper Master is a free download (freeware)!

And many other useful features that give you total control over your desktop wallpaper.