Agreed. The header should be centered. The background gray color clashes. The default forum icons should be replaced, etc.

All of that said, what really makes a forum work is the content. If the content can draw/create a community, then the window dressing becomes less important.

I should also mention that there are a number of vBulletin-related sites for tips and styles. We don't promote or endorse any of them here, so I won't post the URLs. Just do some web searches or PM me.