Spoiler:
Who do you think got the trophy head?
Crazyhorse got the hide but I'd like to think Bronson took home the head maybe that is how he was going to "settle up" with his partner (Jack Warden's character).
He's not fair, you're not fair, the white buffalo's not fair!
Hickock (Bronson) wearing shades concealed him and made his character appear dark. Charlie (Jack) portrayed a darker character still and had a glass eye. None of this carries much significance.
It was the Worm aka Crazyhorse who got the death blow from his arrow shot so I figured he was taking the whole carcass. The white men don't appear taking anything. Having the bust would likely recall those scenes of a stampeding earthquake but you could be right, he'd just want to sell it.