Well, it's more of a client hex than a graphic mod.
Do this at your own risk.
Anyways, here goes:
Open your client in a hex editor(xvi32), and look up this hex string.
83 C4 04 84 C0 0F 84 E3 00 00 00 8B 96 24 02 00
Replace it with this one.
83 C4 04 84 C0 E9 E4 00 00 00 90 8B 96 24 02 00
Note: You'll have to SEARCH and REPLACE it TWICE. If you fail to do that, either the suit won't go away, or your character's head won't align with the body anymore.
What this will do, is IGNORE the Game Master suit, you'll wear whatever clothing your job actually is.
You'll still have the magical right-click powers, and Yellow name/text.
Didn't check what happens with the GMs without rightclick powers. (i.e: GMs inside <admin><yellow> blocks)
Tested on RagRE 2011-01-11a, don't know about the rest of the clients.
Hope it works out for you.
Shag's post in [Resolved] Game Master Sprite was marked as the answer