How do I automatically cycle through backgrounds in Ubuntu 9.10?

"You can do this without installing additional software. Simply use gconftool with a little shell script trickery (untested):

#!/bin/bash

while [ 1 ]
do
find /path/to/wallpapers/folder -type f > ~/walls.txt
count=$(cat ~/walls.txt | wc -l)
for files in $(seq $count)
do
file=$(cat ~/walls.txt | head -n $files | tail -n 1)
gconftool-2 --type string --set /desktop/gnome/background/picture_filename ""$file""
sleep 300 # wait 5 minutes before changing again
done
done

you'll need to change the /path/to/wallpaper/folder accordingly. This will go through every image in the folder, changing every 5 minutes. Once they've all been used it will start at the beginning again, and regenerate the file containing the names of the wallpapers to include any new wallpapers."

"From here

Configure Desktop gives the option of a slideshow composed of any backgrounds you choose.

.

you can user wallpaper-tray is nice and easy. The options are very similar to kde's desktop background options."