1) You've got too many forums. Trim it back by combining inactive forums. The KISS (Keep It Simple, Stupid) mantra applies here.
2)Your title banner is too big, make it shorter. As it is right now when someone goes to your forum all they see is title and advertising -very little forum. You need something to entice the visitor. Notice how the banner here at AO is a bit over 100 pixels high.
3) Since you're using the free invisionboard, your best bet is to play around with the template colors. Try out some color combinations that make you happy. Avoid dark fonts on dark backgrounds and light fonts on light backgrounds.