There's only one background image allowed on per element. But you could use pixel measurements as well, if this is what you're looking for. Pixel measurements translate into CSS Image Sprites. In example:

Url(bg.png) repeat-x top -30px;

This would use the background image of the top edge, 30 pixels into the image. Other than this, there's no other way to use more than one background image. This can only be accomplished using CSS3.