Wallpapers are same on each workspace in ubuntu default,here is a way to make wallpapers different on each workspace,but you must have installed CompizConfig Settings Manager,and you will lose any shortcut on desktop,so install Avast window Navigator for better results.
Update 1: Due to bug, different wallpaper doesn’t work in Ubuntu 10.10 Maverick. But now it works in Ubuntu 11.04 Natty. For some can’t find Wallpaper in CompizConfig Setting Manager, type this in terminal to install plugin-extra:
sudo apt-get install compizconfig-settings-manager compiz-fusion-plugins-extra
1.) Now go to System–>Preferences–>CompizConfig Settings Manager(Advanced Desktop Settings)
tick Wallpaper on(if not go to Desktop Cube,click to go to Appearance–>background images),and click on it to go to its configuration page,click New and add the wallpapers you want
2.) Open a terminal window and type code(Ubunut 11.10 user skip this and see the update below):
in the next window,go to apps–>nautilus–>preferences and deselect show_desktop on the right of the window
then close it
Search and install Advanced Settings (Gnome Tweak Tool) in Ubuntu Software Center, and then launch it. Turn off “Have file manager handle the desktop” in Desktop.
Following is my wallpapers: