Is there a Zbrush 3.1 Icon Set for ZTL, ZBR, etc?
Nope.
no but you can always make your own icons, of anything and assign them to file types, you do this through the folder, file types tab. i have a bunny for my zbrush icons and robots for all my image files, go crazy with it, its fun. 
OK aurick
Thanks spaceboy412:)