So the Justice League movie is coming out in 2017, and then the DCCU will be established for the new 3 years. Several of the DC cinematic universe characters have been cast, but for the important few that haven't, I have came up with my castings.
Arrow is amazing, but unfortunately we cannot have him on the big screens. He is essentially Batman and extremely bad***, but I believe for the big screens we need a young, comic, Oliver Queen. I think Alexander Ludwig could play him, he is young, and he could be the on-screen adaptation of the new 52 version, which I think Synder is going to use as inspiration for many of the characters origins.
I think this is one of the smaller characters with a bit lighter roles, so I chose Olivia Thilby, who is older than Alexander Ludwig, which is slightly awkward for the role, but apparently in the new 52, she is older than him.
Talia Al Ghul
I think Serinda Swan should get the role, she has played Zatanna in Smallville, but I think she can pull this role off. Another reason I casted her was her eyes, she could claim to be Middle Eastern with those eyes.
For Billy, I think Frank Gingerich, the boy from Grown Ups and Grown Ups two, could play him. He would only be 13 or 14 when playing Billy in Shazam in 2019.
For Shazam/Captin Marvel, I think Alan Ritchson should play him, because he doesn't seem like too serious of a guy to crack jokes as a ten year-old. And he coincidentally has the same hair color as Frank Gingerich.
And that concludes it.