forumdisplay.php?f=x ... Changing 'x'

[Lost_Prophet]

This is a slightly odd request perhaps, but one of my users is attempting to make a forum-dependant signature script (that displays a certain sig image depending on the forum you're in)

He's basically - to my knowledge - doing an "if in this forum, display image X" style script. However its pretty tedious with all the forum numbers, and we have 160 forums including catagories

Is there a way to:
a) Alter the number that comes at the end of a forum (forumdisplay.php?f=x) to anything - eg abc01, abc02, etc.
b) Assign some sort of 'mask' to a set of forums so that they all display the same URL