Heres is you answer Wallpaper Master. This program is a very lite wallpaper changer up to 5000 images, can change when windows starts, every (X) minutes, or ratings to choose an interval, and changes order, in shuffle mode, or randomly according to rating. Will automatically choose between Resize, Tile, Center or Stretch or a custom set size.
Just download it and watch the video below. The pro version is the same as the free just once you register it will unlock.
Support for many more image types (GIF, PNG, JPEG-2000 (JP2), TGA, WMF and PCX images).
Max wallpapers increased to 64000 per category! (Rather than 5000).
Now includes a fullscreen Slideshow mode and a Screensaver.
New MultiMonitor support! - Change wallpaper on your dual monitors.
Automatically change wallpaper at specific times of every day.
Skip a cycle if CPU load is too high (useful for when playing games).
Position portrait images to uncover icons.
Apply a simple effect to a certain percentage of wallpaper shown.
Ability to overlay the image's name onto the wallpaper (watermarking).
A huge performance boost and much improved user interface.
Many more options and more customizable!
I have the pro version and for 20 dollars i think its the best money i have spent ever and that was 5 years ago.