Trivia: When the painting in Lex's office is turned upside down and the demons are descending from the sky, they bear a striking resemblance to Darkseid's Parademons. A possible/likely foreshadowing for the Justice League movie.
Trivia: In the film General Zod's home is identified as being Kandor, a city on Krypton that was eventually stolen by Brainiac, shrunk, and hidden in a bottle for observation. In the comics, both Zod and Jax-Ur (who was referenced in Man of Steel) lived in Kandor at some point.
Trivia: The lightning tornado dream sequence echo voice thing is the DC Extended Universe version of The Flash, The Flash appearing in mysterious form, kind of like a dream, and possibly from a different point in time, is very much a reference to Crisis on Infinite Earths where Flash was appearing to various heroes trying to warn them of what was to come while he was busy dying later in the story fighting the very same threat.
Trivia: Batman's regular and armoured suits in the film are very close in design to those from Frank Miller's The Dark Knight Returns.
Trivia: S.T.A.R. Labs is a research facility originated in Superman #246 some 45 years ago, and currently a key component of CW's The Flash TV series. The lab was also the employer of Silas Stone in Teen Titans - and it's Silas who we see creating Cyborg at the lab in that truly spine-tingling video recording on Diana's laptop.
Trivia: When Batman is at Gotham Docks, lying in wait at the wheel of the Batmobile as the Kryptonite is unloaded, the warehouse he is hidden in bears the name Nicholson Trading Co., a reference to Jack Nicholson's legendary take on the Joker in Batman.
Trivia: The spaceship held by Superman has the number 003 as a reference to 300, another Zack Snyder film.
Chosen answer: It is Flash. He is wearing armour because of whatever has transpired in the future. He often wears an armoured suit in dire circumstances in the comics.
Also, if you look at the bottom of the image frame you can just make out the Flash icon on his chest piece.