Topic: Set background


I've got a problem I've been tumbling with for almost a full day now, so really hoping for some help here!

I have set up a simpleviewer compact gallery using flickr to import photos. It's all working perfect.
However I really want to either set a costum background picture to the gallery OR make the gallery transparent, so the webpage from my background would be visible.

Is this possible? And more important, how?

Help will be much appreciated!  :)