Admittedly, I'm really just a Batmaniac, rather than a huge fan of DC as a whole (I know, sue me), but I know Batman like the back of my hand, and I'm also a dedicated cinephile, meaning the whole business of movie making and acting fascinates me. That being said, I wanted to make sure I put my knowledge of these things on the table and create a truly original fancast; avoiding the casting choices that everyone else (including myself, in the past) have made. I'll list older/alternate casting I have made as "Understudies". In addition, I've also got a couple of cast members who are switchers, as in they can fill one or the other of two roles... so watch out for those.
And here... we... go.
Directed by Denis Villenueve (Prisoners)
Score composed by Jonny Greenwood (There Will Be Blood)
Billy Crudup (Almost Famous) as Bruce Wayne/Batman
Understudies: Guy Pearce, Joaquin Phoenix, Alessandro Nivola
Bruno Ganz (Downfall) as Alfred Pennyworth
Understudies: F. Murray Abraham, Malcolm McDowell
Geoffrey Rush (Shine) as James Gordon
Understudies: Martin Sheen, Kenneth Branagh
Brie Larson (Short Term 12) as Barbara Gordon/Batgirl
Understudies: Jennifer Lawrence, Elizabeth Olsen, Alicia Vikander
Michael B. Jordan (Fruitvale Station) as Dick Grayson/Nightwing
Understudies: Ben Barnes, Daniel Zovatto
Jack O'Connell (Starred Up) as Jason Todd/Red Hood
Understudy: Ezra Miller
Tyler James Williams (Dear White People) as Tim Drake/Red Robin
Understudies: Dylan O'Brien, Thomas Brodie-Sangster
Evan Bird (Maps to the Stars) as Damian Wayne/Robin
Understudies: Jasper Newell, Isaac Hempstead-Wright
Monica Bellucci (Irreversible) as Silver St. Cloud
Understudies: Tilda Swinton, Lucy Liu
Lara Pulver (Sherlock) OR Shannyn Sossamon (The Cyclist) as Selina Kyle/Catwoman
Understudies: Natalie Dormer, Kate Mara
Lara Pulver (Sherlock) OR Shannyn Sossamon (The Cyclist) as Talia al Ghul
Understudies: Olivia Wilde, Emily Blunt, Gemma Arterton, Yasmine al Massri
Oscar Isaac (A Most Violent Year) OR Chiwetel Ejiofor (12 Years a Slave) as Ra's al Ghul
Understudies: Daniel Day-Lewis (he'd never do a superhero film), Chrisoph Waltz
Oscar Isaac (Ex Machina) OR Chiwetel Ejiofor (Dirty Pretty Things) as Dr. Hugo Strange
Understudies: Robin Williams (R.I.P.), James Spader
Ben Whishaw (Perfume: The Story of a Murderer) as Dr. Jonathan Crane/Scarecrow
Understudies: None
Adrien Brody (The Pianist) as Dr. Kirk Langstrom/Man-Bat
Understudies: James Ning, Andy Serkis
Terence Stamp (Unfinished Song) as Dr. Victor Fries/Mr. Freeze
Understudies: Mark Strong, Ben Kingsley, J.K. Simmons
Sarah Snook (Predestination) as Dr. Pamela Isley/Poison Ivy
Understudies: Christina Hendricks, Alexandra Daddario, Gabrielle Union, Rene Russo
Jack Plotnick (Rubber) as Edward Nigma/Riddler
Understudies: Kenneth Branagh, Andrew Scott
Rufus Sewell (The Illusionist) as Roman Sionis/Black Mask
Understudies: Sam Rockwell, Giovanni Ribisi
Vincent Cassel (La Haine) as Victor Zasaz
Understudy: Aaron Paul
Viola Davis (How to Get Away with Murder) as Amanda Waller
Understudies: None (let's be honest, there really never was another choice here)
Ben Foster (The Messenger) as Floyd Lawton/Deadshot
Understudies: Norman Reedus, Mads Mikkelson
Michael Kenneth Williams (The Gambler) as Slade Wilson/Deathstroke
Understudies: Joel Edgerton, James Caan
Jake Weary (It Follows) as George Harkness/Captain Boomerang
Understudy: Jon Bernthal
Raymond Cruz (Breaking Bad) as Chato Santana/El Diablo
Understudy: Eduardo Noreiga
Richard Brooks (Firefly) as Eric Needham/Black Spider
Understudy: Donald Glover (consolation for not getting to be Spiderman, I guess...)
Takamasa Ishihara (Unbroken) as Chang Jie-Ru/Yo-Yo
Understudies: None
Alicia Vikander (Ex Machina) as June Moone/Enchantress
Understudy: Ivana Baquero
Gemma Ward (The Black Balloon) & Amanda Seyfried (While We're Young) as Lime & Light
Understudies: None
Taryn Manning (Orange is the New Black) as Dr. Harleen Quinzel/Harley Quinn
Understudies: Zooey Deschanel, Jena Malone, Juno Temple, Rosamund Pike, Christina Ricci
Ethan Hawke (Predestination) as Joker
Understudies: Christian Slater, Vincent Cassel