Tiled BG Image – Editing CSS / K2 Theme

Hey, I want to add a tiled image as the background in WordPress. I’m using the K2 theme, but I’m guessing the process is similar no matter how I do it.

I’m fairly sure in K2 I should open “style.css” from the theme editor. Does anybody know where I could locate the BG info, and how I could change it from a color to a tiled image?

Thanks!