While Zack Snyder and Warner Bros. were making Batman v Superman: Dawn of Justice, the plan was to release a two-part Justice League movie as a follow up. Those plans changed after the negative reaction to Batman v Superman and Justice League was restructured as one movie. But now Zack Snyder has revealed a Batman v Superman easter egg that would have made more sense after we saw Justice League: Part Two.
A fan on Vero posted the Batman v Superman photo above and said that he never noticed the crosses in the background before. Zack Snyder replied and said, “that’s a reference to Justice League 2”. He then added “until it wasn’t,” likely referring to the movie’s cancellation.
In October 2014, Warner Bros. announced Justice League: Part One for November 17, 2017 and Justice League: Part Two for June 14, 2019. Maybe someday Snyder will reveal what that easter egg in Batman v Superman was referring to in Justice League: Part Two. For now, feel free to speculate in the comments below.