Just set the time of changing the wallpaper. It will automatically change the wallpaper at the fixed time. It also has the option to change the wallpaper at windows startup. There are many other options. just try it out.
Allows you to easily change desktop wallpaper.
Wallpaper manager:cycle JPEG, BMP, GIF image
BloodFalls Wallpaper Halloween Wallpaper
Good Wallpaper Changer for fun desktop
Wallpaper Manager 2.0.524.0
A wallpaper cycling tool for multiscreens.