I'm going to have to disagree with Nigel on that. It took me two weeks to customize my forum into my website's layout theme. I had to figure out where all the code was hiding, and actually it taught me quite a bit about CSS, php, and html just trying to change things. My final product:

friendshipbeading.net/forum/index.php

Quite different from the default look right? To get rid of signing up forms (I also didn't want my users to sign up), I simply commented out the links at the top right that said "Register" and "Login". LOL!