I've added avatars in last post on my site. You can do it either for the forum list or/and for the discussion list. Click on the first link in my sig and check out the forum to see it in action. I think it brings a more facebook-like feel to the site. I don't know how it would work out on your site though but just letting you know about it in case you feel like experimenting one day and want something to try out. I'll show you how in this thread if your curious or pm the code to you.