Is there any way to set a background for a frame, or at least an Inline Frame? Then when people views pages in that frame, it will have the background of the frame.

You just have to add the background code to the page(s) that appear in the frame...

Oh, I meant something like, instead of having to put the code on every page, you can just put it in the frame, and then you can change how you want your page to look very easily without going through each page again.