Cheyenne has had a rough life as a native and eventually turned to crime.
Django is obviously a marksman, perhaps he fought in the Civil War, before turning to crime.
Ghost looks like a career criminal, probably started picking pockets at a young age.
Doc reminds me of Maverick, a card player and gambler type who's trying to get in on a train robbery, not usually his type of scene but he's a smart guy who's always a step ahead.
Belle reminds me of Annabelle from Maverick and might even be based off her -- a slippery shyster who uses her good looks to distract from her devious purposes. Like Ghost, her life of crime probably started at a young age.
Tuco looks like he's actually part of the train crew, almost "riding shotgun" to thwart bandits. Maybe he was, but he's one of them now.