Back in 2008-9, Warner Bros. was developing a Justice League movie with George Miller directing which was to be titled "Justice League Mortal."
The film was going to be shot in Australia, but due to the writers' strike at the time as well as film-budget issues and the fact that Christopher Nolan didn't want two different Batmans on screen (Batman Begins was released in 2005) saw the "Justice League Mortal" movie get the axe.
The movie got so far as having a cast, which consisted of: Armie Hammer (Batman), DJ Cotrona (Superman), Megan Gale (Wonder Woman), Adam Brody (The Flash), Common (Green Lantern), Santiago Cabrera (Aquaman), Teresa Palmer (Talia Al Ghul), Zoe Kasan (Iris Allen), Hugh Keays-Byrne (Martian Manhunter) and Jay Baruchel (Maxwell Lord).
Concept art was developed and the actors even tried on costumes (Armie Hammer talks about his Batman suit here), but alas, "Justice League Mortal" was never meant to be.
The good news is that you can read the "Justice League Mortal" script for yourself as it's presently on scribd.
Check out images and art associated with the film as well:
Superman Vs. Wonder Woman storyboards: