Having an ability to equip troll skull as a helmet (pumpkin-like) would be pretty awesome, it should have some low/mid-tier armor class and possibly give str/con/masonry.
Another possible use is a high-tier helmet that is made of troll skull and high tier materials which will look as something similar to 2nd (full skull used as a helmet) or 3rd (skull is needed as a reference to make horrific, demon-like look) screenshots:
EDIT: For the helm on the second screenshot Troll Hair can be used as one of the materials. While we are on topic, what about troll hide capes...