How to make uneven background? - outerspace or Grunge BG

These two websites have uneven looking background. Rawkes doesnt have that much of space show but i have seen websites having stars as background. The grunge background of mattbrett is also unsymetrical.
I find no other way then putting a huge image without repeating elements on the page. But thats a prob aint it. too much loading time, un even look on various resolutions. It must be a repeated element. How do they make it?

Need some help.

thanks
-Ray Lead

Use tiny image in backgroud css repeation.Large image always take much time.