Holly Hunter has joined the cast of the untitled Superman vs. Batman movie, as well as Callan Mulvey and Tao Okamoto, according to The Hollywood Reporter.  All three will appear as new characters created for the movie.
 
Mulvey can currently be seen as Scyllias in 300: Rise of an Empire, and has a minor role as Jack Rollins in Captain America: The Winter Soldier.  Okamoto played Logan’s love interest Mariko in The Wolverine.
 
The Superman vs. Batman movie is slated for May 6, 2016 (see "Ouch! 'Superman/Batman' Movie Bumped to 2016").