This code is still in testing stage. If you notice it is not working, report in a comment on here. Thx.
On demand I created this code that allows a background switching. Just change the piclink value (note: leave the brackets and DO NOT use additional brackets within the brackets. Just put the URL to the picture between the too ''.
What exactly does this code do?
When you use it you can rightclick and the page background will change into a different one. On the second click it should change back to the old one. Another click to the different one again and so on.