Besides making the forums more fun and colorful, I'm guessing these badges are there to also promote the friendly atmosphere, civilized behavior, obeying the forum rules, etc. That said, it might be a good idea to have one or two badges that can be won fairly easily, so as to motivate people to participate in various other forum activities.
As far as badge suggestions go, I have a couple of those for everyone's consideration:
People Person - given to members who have <number> or more friends on the forum.
Game Master - for those active in the RP sections. Perhaps there could be a thread every few months for members to nominate the best forum RPs and the member who started the "best forum RP" in that period would get this badge.
I've noticed there's a new "Helpful" badge. My last suggestion would be that either this one, or the "Notable contributor" badge be also given to members who have contributed to the forums by making a significant amount of avatars/signature images/banners/etc for their fellow members.