planchettebd on "Is it possible to have changing background for my site."

Hi. I run wordpress site where I publish my webcomics.

http://www.planchette.ca

I used might background image to display a drawing of one of my project in the left side of the screen. I was wondering in it would be possible to make the background randomly select beetween several images (One for each of my project)so that the background would change every time someone visits the site. If it is possible, how could I code into the CSS editor.

Thanks