Is there any use for those skins that you get off the beetles & hulks?

He'll offer to make you a shield out of the beetle hide I think (not that good though, only Druids benefit from it), and will have an Umber Hulk armor on sale.

-Wrath

somehow you can trade them Dirty Lew for the Umberhulk armor. i'm not certain, but i think you have to have a high charisma and probably be Male. (Females get a discount on the rhinoshield).
BTW, Nym can enchant your shield in two different ways depending on how you haggle (and how hott you are). Also, I think Orrick can enchant it too.