Okay, I have a tiling background image applied to the body. Then I have a another graphic horizontally centered as a div. All my pages' content will rest within the boudaries of that div, but I can't figure out how to vertically center the graphic. Can anybody give me a hand?

Actually, you cant. Vertical centering of an element is not possible by a "one-line-code", but with some code-hacking you can fix it.

Have a look at this page (dont worry, you do not need to know norwegian to understand this one), and watch the sourcecode:
http://studentersang.no/bjarne/vertikal.htm