Straight up: Spoilers here for Justice League, although nothing you wouldn't have guessed from marketing. You've been warned, however. Here goes: Superman comes back. The Death of Superman was obviously a big influence for the film, with the Doomsday story happening in Batman v Superman: Dawn of Justice. There was a big part missing in the film from the iconography of the story. The black suit.
Rumours have flown back and forth about whether there was ever a such a variant of the Superman suit in the film, but it seems we have solid proof now. Speaking to Inverse (vis Batman News), the film's cinematographer Fabian Wagner has stated that the suit did exist and scenes were shot with it. It appears that the take over from Joss Whedon saw all that cut though. Wagner confirmed:
There were [scenes shot]. It's a cool looking costume. Sadly, we didn't see that either in the final cut.
He later added:
Zack takes his time with telling the stories, and I've always liked that about his movies. There are a few scenes that I was very much looking forward to seeing which unfortunately got cut.
He also talks about being disappointed other scenes got cut, including the one where Alfred says "They said you'd come" from the final trailer.
People will pick over how much of this movie is Whedon's and how much is Zack Snyder's for a long time I imagine. It really does seem like a lot changed around.