Symbolism, Imagery, Allegory
Don Aranda, the owner of the slaves in "Benito Cereno", is put to death by Babo and then his skeleton is hung from the front of the ship and the words "Follow your leader" chalked by it. Yeah, that's not creepy or anything.
The skeleton is hidden for most of the story, but towards the end the ship shifts "suddenly revealing, as the bleached hull swung round towards the open ocean, death for a figure-head, in a human skeleton." (3.372)
So, obviously, the main thing this shows is that Melville has a taste for horror-movie shockers. If he'd lived today, he might make Hollywood slasher films. Picture it: Moby Dick the 13th : Jason and the Whale. We'd go see it.
Beyond that, though, the revelation of the yucky skeleton comes at about the same time as Delano realizes that the slaves are in control of the ship. So it's a vivid way of showing that all is not nice and happy, that instead the ship is run by evil Babo and his regime of horror and death. Aranda's corpse shows the shocking cruelty of the black slaves, and demonstrates that their lust for death knows no bounds; they want all the whites to follow Aranda to death.
Or that's one way to look at it.
You could also see the evil here, though, as belonging not to the former slaves, but to the slave-holder. Aranda was a merchant of death; he traded slaves. Putting him on the prow shows not that the slaves have made the ship a ship of death, but that it was always a ship of death. "Follow your leader" could mean, not, all white people should die, but rather, white people who trade in slaves are sailing a ship to hell.