People can loot or buy helmets (from other players, if not from NPCs). People can even craft helmets and sell them. People can even craft magically resistant helmets, if I remember correctly...
But custom clothing is currently not yet available. The system how armor is managed is still rather basic, therefore many different kinds of clothing (especially with different shapes, like dresses or robes) are rather hard to implement. And yes, this has been discussed before.