Wallpapa is a wallpaper manager for Windows that will rotate your background image, so you never get bored.
Wallpapa has a simple interface. You add folders with wallpaper images you like, choose whether to change at startup, how often and so on and it will then manage your wallpaper automatically.
Most image formats are supported, so you shouldn't need to do any converting of pictures to use them. You have to supply the wallpapers yourself, and while it would have been nice to have some supplied, it takes the tiniest amount of searching to find and save backgrounds you like.
Wallpapa is a really simple and lightweight wallpaper rotation application, which can help keep Windows desktop looking fresh!