Michael Fessbender as Batman/Bruce Wayne.
John Hurt as Alfred.
Jamie Lee Curtis as Dr. Leslie Thompkins.
David Finlay as Mad Hatter.
Doug Jones as Basil Carlo/Clayface.
Kevin Costner as Kirk Langstrom.
Scarlett Johanson as Harley Quinn.
Kate Beckinsale as Zantanna.
Mary Elizabeth Winstead as Catwoman/Selina Kyle.
Michael Rouke as Croc.
Guy Pierce as BlackMask.
Ben Kingsly as Dr. Hugo Strange.
Adriene Brody as Professor Milo.
Isla Fisher as Poison Ivy.
Jon Voight as Rupert Thorn.
Michael Madsen as Harvey Bullock.
Michelle Rodriguez as Officer Rene Montoya.
Philip Seymore Hoffman as Penguin/Oswold Copplebot.
Gerald Butler as Maxamillion Zeus.
William H Macy as Karl Rossom.
Debbie Carrington (the midget hooker from Total Recall and The Garbage Pail Kids movie) as BabyDoll.
Kevin Spacey as Mr. Freeze.
Hugh Jackman as Anthony Romanus.
Rachel Weisz as RedClaw.
David Cronenberg or William Dafoe as Dr. Emile Dorian.
Robby Benson (Beauty and The Beast's Beast) or James Avery (Uncle Phil on Fresh Prince and also the original voice of Shredder in the old turtles toon and Fang on the anime classic Fist of the North Star as he was that guy who turned his body to steel) as Tygrus's voice.
I like your choices, I'd love to see at least Zatanna in live-action.