Newly discovered concept art by Robert McKinnon shows the ruthless mastermind in his prison cell, likely plotting an escape or Superman's demise or both.
Check out the image below:
Eisenberg was announced as joining the cast of Justice League early in pre-production, though the extent of his role was unknown. After Snyder stepped away from directing the reshoots due to a family tragedy, Joss Whedon came on board. New rumors popped up that Luthor was cut entirely from the film, possibly indicating that it was always a smaller role.
Eisenberg did make the finished film, however, as revealed in the post-credits scene. In it, Luthor is shown meeting with Deathstroke (Joe Manganiello) on his yacht after escaping prison and leaving a body double in his cell. Luthor proposes teaming up with Deathstroke, possibly teasing the formation of the Injustice League in the potential sequel.
Luthor's cell from Batman v Superman: Dawn of Justice and Justice League didn't have the luxuries shown in this concept art. Perhaps good behavior afforded him some decent reading material and his own not-so-private bathroom.
McKinnon also worked on the production of Batman v Superman, creating the concept design for the weaponized Metallo that was almost featured in the film. Just like the Luthor scenes, there's no telling how significant these aspects would have featured in the film. Eisenberg's Luthor was met with mixed reception among fans, like almost every other aspect of Batman v Superman.
Perhaps the character was meant to play a major role in Justice League before the fan response caused a change in the script and story.
As it was, Justice League was packed to the brim in its runtime. With all of the heroes coming together, Steppenwolf's plot to obtain the Mother Boxes, and the resurrection of Superman. Including a subplot of Lex Luthor attempting to escape from prison or turn the situation to his advantage probably would have been too much for the film.
Justice League is now available on Digital HD and will be available on Blu-ray and DVD on March 13th.