Individual dual monitor shuffled wallpaper?

I've come up empty after doing some searches, so I thought I'd ask here...

With a dual monitor setup, I'd like to have different wallpaper on each monitor. On top of this I'd like each desktop to change occasionally (20 minutes?). Is there any software out there that does this?

Basically, I want two folders full of images. Each folder will contain wallpapers for a particular desktop. Each desktop would be set to change wallpaper after a certain amount of time. Setup could be a simple INI file in the image folder, or within the program itself.

P.s. Animated GIF support would be nice but not necessary.

Thanks for the info. I'd look a Bionix, but I don't trust any company that offers a crippled free version and doesn't tell you how much the full version costs.

Almost as soon as I posted I decided to try Display Fusion. I'd seen it before, but thought it was overkill. I still think it's overkill, but does what I want so far... Not sure if it's worth $25 just to rotate my wallpapers though.