Topics that have lots and lots of posting... or lots and lots of viewers... or the combination of those "like, lots of viewing and no posting" could receive some kinda special icon, or something like that.
For instance... a Topic that is already like a week online and was only visited 2 or 3 times, gets a "frozen topic" icon.
A topic that´s new and has lots of viewing, receives a "big eye" Icon.
A topic that's new, has lots of viewing AND posting, receives a "topic on fire" icon.
Topic that is very old, but keeps receiving more and more posts, receives a "phoenix" icon.
A Topic that's very old and no one seems to put a reply to it for a long time, has a "mummy" or "spiderwebs" icon.
And those for like, automatic configuration. 'cuz the manual Icon system I already have installed...
Anyways, you can play a lot with the statistics of the topics, ... these automatic icon system can work on foruns and users too... it´s a quick, nice and pleasant (visual) way to know more info about the topic...