Via a quick, and utterly unmysterious post, GRRM has revealed who has been cast as the wildling raider known as the Lord of Bones, more commonly mocked as Rattleshirt: Edward Dogliani.
Rattleshirt is one of the chief wildling raiders at the time of the novels, having taken the name of Lord of Bones from the bone-armor he wears (including a helmet made from a giant’s skull). In the novels, he’s described as shorter and scrawnier than his armor makes him, and has an ill-favored look to him. Suffice it to say, he’ll be an antagonist for a certain popular character as the story goes forward.
Dogliani’s CV and a few headshots can be found at the agency website where he’s represented, Marcus and McCrimmon.