I'm pretty familiar with phpBB software, and there's a lot of great modifications that are easy to install out there. A Shoutbox alone can change the experience of using a forum quite a bit. I think something other than the phpBB default skin would be nice to look at, and giving the forum a look that reflects Jetpack is also very easy to do.
As far as content, sub-categories for sections will help to clean up thread lists and categorize threads further into easy to find topics. For instance, putting a sub-categories for Marvel, DC, and Indie inside the Comics category will cover most comic discussions and leave the General Comics category as a place to read staff articles or what have you.
I second the Video game section as well.