How do I get multiple headers and backgrounds?

I currently have the comic easel theme, and I’ve got the background and header stuff for that down pretty solidly. But I’ve got parts of my site that are centered around different projects, and I’d like it if I could make the headers and backgrounds for those pages more accurately reflect them.

I haven’t started really working on the header part, but I installed the background manager plugin. I’ve had some mild success in that it will let me have no more then two backgrounds (i can work with two, though more would be appreciated) but I don’t know how to change it from the standard easel background of black bricks to something I’ve drawn. On the separate pages it will let me choose between the two image sets I have for the backgrounds under the manager I installed, but it doesn’t actually seem to do anything.

So I’m going to assume I have to fiddle around with the appearance editor, but I really don’t know the first thing about CSS, so any help would be greatly appreciated.