Something I have seen on many forums are a sort of "daily/weekly spotlight"... might be a suddenly popular thread in offtopic, a screenshot compilation of particular creativity, a guide that is genius, or a simple question nobody has asked yet in general discussion being researched.
Community highlighting like this promotes many more and healthier moments of fame for people to vie for, since you dont get to coast with your old achievements and must be always coming up with good quality stuff to get back. Also gets threads that should get feedback their due!

Doesnt have to be one thing a week. You could collect a number of threads that surpass the average and put them up on the homepage every week. I can see two great results from this: promote creative or good forum usage, and give a sample of the community to prospecting gamers looking up the game on google.