I've seen a few different tags going around e.g. in this tourney: http://warlight.net/MultiPlayer.aspx?gameid=1957112
But I've never seen more than two of any these tags at one time. The tags are probably just like pwn or STS if anyone remembers them (I think they changed names but are still around).
I think if there was another significant clan out there we'd know about it.
Oh wait, remember this guy? ----->> [Chibi](http://warlight.net/Profile.aspx?p=355172199
His "Guild" kinda sounded more like a cult to me but he looks like he's gone anyway. That was the closest to another clan as we've gotten I think.