Random header_bg or different image for different page

I created a website with appphone and I made ​​some changes to the css.
I edited the file "header_bg" in MainPage and I thought I could change this file at random, so that always appear different each time the visitor enters the home.
Can I use some function to manage the random background?

Alternatively,
I used this function: http://www.gavick.com/magazine/sites-background-change-according-to-subpage.html
changing bg_images $ in $ mainpage but does not change the header_bg but the underlying background.

how can I do?
thanks

Hi

Sure. I have a php function selecting backgrounds randomly for pages. But you can always make it simple way and use page class suffix and attache a different background for pages wih this suffix.

Or you can attaché a module with a CSS code loading background image to any page desired.