We knew about this? Gotham is sort of a Batman: Year One Minus Ten. Bruce Wayne is an adolescent, James Gordon fights corruption in the GCPD, and Gotham's future bat-villains are just geting their start.
Ben MacKenzie as Detective James Gordon
Robin Lord Taylor as Oswald Cobblepot/The Penguin
Sean Pertwee as Alfred
Zabryna Guevara as Captain Essen
Erin Richards as Barbara Kean, the future Mrs. Gordon
Not cast yet:
Young Bruce Wayne/Batman
Could be interesting, I always found the Jim Gordon stuff in Batman: Year One to be the best part of the story.