It would give the game more customization.
Ideas:
Gold hoarder necklaces: small captains chest, a key (not the gold hoarders key but some variation), a gem of various colors with gold outline
OoS Necklaces: various skulls (obviously), a small oos lantern that kinda glows, etc
Merchant necklaces: a small crate of exotic silks, spices, little ship, etc.
Pirate legend necklaces: A fort key, small athena chest, etc
Devils Roar necklaces: flaming rock, devils roar alliance necklace, etc.
Other ideas?