Multiple Layers in Backgrounds

Hi there,

the image you have on the frontpage of the NO8 theme
is floating on top of the blue background.

My question: is it possible to add a layer ON top of that image?
So you get an even more dynamic effect when scrolling down?

For example: I have a image that is floating on top of the background.
Can I make other elements float on top or behind that image?

Thank you.

Laurens.