After playing America's Army, it was nice to know when an admin was present to protect the players from idiots. I believe mahnsawce's Admin Icons plugin (for AMXX) is a good idea. However, his version was for Natural Selection. So, if this were made a standard through SM, then admins could have this option for any Game Mod.
Suggested CVar:
1. sm_adminicon 1/0
Also, if this idea is accepted, several Icons should be made to provide a visual difference between Admins with certain levels (AdminMod-esque) or even to discern between Clan Members and Allies (who have been granted low-level admin rights). And I think FreeCode is more than capable of creating some quality icons.