Saint Liberatus was a Catholic monk in the Vandal kingdom of Africa. Huneric, the Vandal king, invited seven monks to Carthage and offered them gifts if they would endorse Arianism. They refused. He had them chained up and thrown into a dungeon. This attracted the attention of Catholics in Africa and the monks received many visitors. Huneric was unamused by thus and ordered them to be put in an old ship and burnt. The monks cheerfully walked down to the shore, where the boat refused to catch fire. Annoyed, frustrated, and not taking the hint, Huneric ordered the monks' heads bashed in with oars. Then their bodies were thrown in the sea, but the sea refused to keep them, and washed them ashore, where their followers found them and buried them.
Can't find an image of Liberatus, but apparently this is a picture of Huneric.
I guess this costume is all about the head injury. I should probably have tried to find a saint with better costuming possibilities, but I'm still two behind and didn't want to waste the research.
 The Vandals, a Germanic people, had invaded and conquered the Roman Province of Africa in 429 and had their Capital at Carthage. The Vandals were Christians, but not Catholics; they subscribed to the heresy of Arius.
 I remember reading somewhere, although I now can't find it, that the Vandals liked to paint things black; the Goths, a related people, preferred blues and greens.
 It's to do with the nature of the Trinity.