Something I always wanted to have in Gnome During the years that I used it, it was the detail of being able to put a wallpaper different on each desktop, this in KDE3.5 was really easy to achieve. Unfortunately the only method I found was just a self-deception 
However, this can already be achieved in KDE4… here you will see how to do it, without the need for complicated commands (none actually), or secret configurations or anything like that 
As you can see in the image above, this is a sample of what I'm talking about, those are my four (4) desktops with the wallpaper of each one 
1. Let's go to the configuration panel and select «Workspace behavior«:
2. Once in there, yesWe just have to mark the option «Different graphic components for each desktop«:
3. And voila… we just have to click on «Apply» to save the changes, or simply close the window, the same system will ask you to save the changes 
That's all. Now just change the wallpaper on one desktop, you'll see how this won't affect the rest of the desktops 
regards