4. Bowen Marsh
Strictly speaking, the character of Bowen Marsh has been cast before, though the actor portraying him appeared only in the background in two episodes of season one, was never referred to by name and had no lines. Now that Jon Snow finds himself back at the Wall alongside Sam Tarly, additional characters will be needed to flesh out the scenes involving the Nights Watch as they prepare for the inevitable assault from Mance Rayders wildlings. The confirmation that Janos Slynt (the former captain of the Kings Landing City Watch banished to the Wall by Tyrion Lannister) is returning in the upcoming season suggests that the show will be utilising the story that involves the election of a new Lord Commander, given the untimely death of Jeor Mormont at the hands of mutineers during season three. As an authority figure (First Steward), Bowen (or the likes of Cotter Pyke and Denys Mallister) should be included to deepen proceedings, because what fun is a leadership election with only a few significant candidates?