It turns out that Zack Snyder intended to put a few more characters into the upcoming Batman v Superman, telling Collider that he very nearly threw in scenes with notable Batman rogues Joker and The Riddler.
Snyder said he discussed the move with screenwriter Chris Terrio, but ultimately decided against it. He claims that while both villains have a presence in the film (the Joker especially, judging from the trailers), the decision was made not to include them so that more time could be spent with both Batman and Superman.
It's probably a good thing they ended up cut. The film is looking big enough already, with confirmed appearances from Batman, Superman, Wonder Woman, Lex Luthor, Doomsday, Aquaman, Cyborg, and The Flash. It's also been rumoured that cosmic baddy Darkseid will make an appearance, and Barbara Gordon/Batgirl/Oracle has already been cut from the theatrical cut.
As we already know, Jared Leto is playing the Joker in this year's Suicide Squad. The Riddler hasn't shown up just yet, but Neil Patrick Harris has expressed interest in taking on the role in a future film. He'd have pretty big shoes to fill, though. As awful as Batman Forever was, Jim Carrey was pretty damn perfect as The Riddler.