It's quite a dark theme (black/grey/red).
Losely based it on the color scheme used by www.warhammeralliance.com
Other than that, Well Done!
Also changed it so only forum and topic list use an alternating style. But topic display doesn't use alternating style since there's already enough distinction between posts via header/footer and .postsep.
Also added some custom BBcodes that will display a popup when hovering over items.
The BBcode enhancements are just too cool! Mind sharing the upgraded code to do that!?
Very well done!