5 votesXerexes commented
I would suggest having a fixed set of categories - basically genres that you put each comic into. This will really help if I'm trying to explore say "comedy". Separate from that it would be nice to let the users tag the comics freeform. So Sinfest gets "comedy" as a category AND a bunch of more specific freeform tags from the users.
Some examples of other sites categories would be Clicker.com (what you're doing but for video) at http://www.clicker.com/category/action-and-adventure/
or Good Reads (for books) at http://www.goodreads.com/genres