Well some things that are appreciated, though not necessary with such a system is:
-> Ability to colorize different elements; ie a different color for metals, cloth, leather, etc... for a specific slot. So have golden bangles for the leg slot, but silvery bangles for say shoulders.
-> Different textures applied to same mesh; ie cloth pants could be made of cloth, or have patterns on them or have transparency (ie ripped cloth).
-> Some good old cloth physics; depending on difficulty of implementing such a system. Like a flowy skirt, kind of thing.
-> Pulled down, pushed aside, or crumpled up on the ground.
-> The ability to remove or re-add clothing.