According to Cinema Blend on Dec. 9, it appears that currently "Game of Thrones'" Jason Momoa is currently in negotiations to possibly be an additional character in Zack Snyder's "Batman vs. Superman". At this point, there's nothing more. There is no news currently on what part they would be placing him in even if chosen for the role.
Warner Brothers had no comment even when asked for such information and also Callan Mulvey, known for his popular role in "Zero Dark Thirty" was also another actor being considered for a villainous role. It could only be speculated that Momoa may be competing for the same role as Mulvey.
Momoa had sometime back was also being considered for the role of Drax the Destroyer in James Gunn's "Guardians of the Galaxy" and now Gal Gadot is officially set for the role of Wonder Woman along with actors Henry Cavill and Ben Affleck.
Writer David S. Goyer had finished the first draft of the script and had worked with Snyder in developing the story. "Batman vs. Superman" is scheduled to be released on July 17, 2015 and production is to begin sometime early next year.