instead of asking for skins what about making a quest that only the one seking for the symbol can do something like:
warrior/thieve/archer:enter "xx" cave, kill the gatekeepers and then proceed to next floor and kill xx boss, bring back to the npc a proof of his dead that will be a not tradeable item, and the npc will reward you with the g1 sysmbol of choice.
wiz/priest:enter"xx" tower kill the gate keepers and then proceed to next floor to kill xx boss, then bring his spellbook to npc to receive the symbol of choice
warrior/thieve/archer boss should be like a lesser darkbear but a bit faster, wiz/priest boss should have much less hp and deal less damage with normal hits but will have priest d2 shield and some strong offensive spells like flamewave or fb.