Automatically changing background every hour

[Cameron Hutchison]

I have a bunch of images that I like to use as background (wallpaper)
images. I would like my background to choose from these images at random
every hour and display it. How do I configure gnome to do this?

I was using the chbg program but now something in gnome seems to be
putting up a grey background over the random picture (which is briefly
displayed upon login).

I do not run nautilus in the background or let it show the desktop (I
hate icons on the desktop).

I am using Gnome and Ubuntu 8.04 (hardy).