The image that shows The Flash, Batman, and Wonder Woman all, looking at something that, of course, we can't see.
The description of the photo says that the three superheroes are somewhere in Gotham City where there is a nest of parademons.
We already know that Steppenwolf is supposed to be the main big bad in Justice League, but Kevin Smith goes on to say:
"I call bullsh*t, I think Steppenwolf is a villain of this piece, but I think we're getting Darkseid, and I think that they've been keeping it from us, like the same way we didn't know we were getting Doomsday...I think Darkseid is in this!"
"Just give me some Darkseid...it can't just be Steppenwolf...he's just a pawn!"
He's right - why would Batman be assembling a team of the world's greatest superheroes to defeat...Steppenwolf? Wouldn't he be able to take him down himself or with a few friends - just like Superman, Wonder Woman, and Batman did with Doomsday?
In Justice League, fueled by his restored faith in humanity and inspired by Superman’s selfless act, Bruce Wayne enlists the help of his newfound ally, Diana Prince, to face an even greater enemy. Together, Batman and Wonder Woman work quickly to find and recruit a team of metahumans to stand against this newly awakened threat. But despite the formation of this unprecedented league of heroes—Batman, Wonder Woman, Aquaman, Cyborg and The Flash—it may already be too late to save the planet from an assault of catastrophic proportions.
Justice League is directed by Zack Snyder, from a screenplay by Chris Terrio, and features an ensemble cast that includes Ben Affleck, Henry Cavill, Gal Gadot, Ezra Miller, Jason Momoa, Ray Fisher, Ciarán Hinds, Amy Adams, Diane Lane, Jeremy Irons and Jesse Eisenberg.