the real trick to this is deciding how much customization you want, because each custom body part needs an image layer to itself.
So, I suggest a layer for Face, Hair, Boots/legs, left arm, right arm, body, hat, cape, and a layer for whatever else that doresn't fit intoa that...
from top to bottom the list should be like this ideally:
Hat
Accessory
Hair
Face
Arm
Arm
Boots
Body
with a variable positioning for the cape depending on player direction.