It's not really a secret that Superman will be in Justice League. What is a secret, however, is how exactly he comes back considering he got stabbed through the heart and died in Batman V Superman: Dawn of Justice. When Superman "died" in the comics, he came back sporting a rockin' mullet and a new black costume. The jury's still out on the mullet, but Henry Cavill recently teased that the black costume could be making an appearance in Justice League. One fan has sketched up what Cavill's Superman would look like in the classic outfit, which you can check out below.
And I thought this Superman couldn't look any meaner. This sketch comes from BossLogic, who's made a bit of a name for himself by drawing what certain fan castings and rumors would look like. He's done drawings of actors like Anna Kendrick as Squirrel Girl and Jason Momoa as the Crow to name just a few. One of his latest sketches is Henry Cavill's recently back from the dead Superman. It doesn't take a hell of a lot of imagination to picture a black version of the Superman costume, but the visualization of it is pretty good (there's also a version with a beard).
BossLogic's version does have a few key differences from the black suit in the comics. For one thing, the suit isn't entirely black; the "S" crest in the middle is silver with a few extra silver flourishes sprinkled throughout the body. The comics version also doesn't have a cape. Based on the brief glimpse provided by Cavill, the movie suit looks like it could simply be all black - which is a little boring - but really at the end of the day, all that matters is that he has a mullet. It doesn't even have to be a mullet; just some longish hair that COULD be called a mullet and I'll consider myself a happy camper.
It seems safe to say that Superman will return to his classic red and blue before the movie is over. He's wearing that costume in the group picture of the entire Justice League, plus there was a set photo of Cavill in the red and blue while posing with some visiting kids (though some have reported that the image MGHT be from his Batman v Superman days). It's possible that the costume change signifies Superman's shift in attitudes and officially accepting his role as the protector of humanity. Good old Supes might have a new lease on life when all is said and done.
We'll get to see if Superman has a black costume (and mullet) when Justice League hits theaters on November 17, 2017.