While we were running through missions and bounties earlier today, Malagate pointed out that the Warlock PoE gauntlets looked like they had dead Ghost cores attached to the right shoulder. As he said, “kinda morbid.”

I can't tell for sure, but they certainly look like they might in fact be Ghost cores…

I hadn't noticed this but I think you might be right. I would guess it's more of an honoring the guardians/ghosts who died in the prison than the typical wearing as a trophy.