Is it possible to put two different background pictures into the right and left sides of the following ikiwiki css?

[lessish css theme](https://raw.github.com/spiffin/ikiwiki_lessish/master/lessish.css)

Is it also possible to have a background like this: [http://ysharifi.wordpress.com/](http://ysharifi.wordpress.com/)
or this [tex.stackexchange.com](tex.stackexchange.com)

I am not a css expert so, it would be nice if you could provide some details.