I'm not sure if this is on your to do list Chalex but I think the forum might need some new icons in terms of these ones: and there are some good ones out there e.g. these from DutchDesignz (sorry I go on about them alot)
Hot thread with new posts:

Not hot thread with no new posts and I have posted in there:

Not hot thread with new posts

Not hot thread with no new posts:

Hot locked thread: