They'ze ugly.

In the current system, forum icons mark topics which you have read as blue and unread topics as red (I know).

The shape of the icon marks them as Sticky, Announcement or Topic (regular post). Together with read and unread, that's 2*3 = 6 different icons.

Finally, topics can be marked as Locked, Mine (if you started the topic / posted in the topic) or Hot (if many people are posting there). Given there are 8 possible combinations of that (2*2*2), that leaves 8*6 = 48 different possible icons.

Unfortunately, the system does not work on the basis of overlaying images - however, using layers in an image editor, it shouldn't be too hard to use overlays when creating these icons.

The new icons should have proper transparency (to prevent anti alias problems), be 40×40 pixels in size and preferably a bit starwarsy / science fictiony in nature.

Here's some idea's:

The forum actually also has forum icon for use with sub-forums, but since we don't use sub-forums, I don't think it makes sense to use those.