Notes:

Ok, jokes aside these are my guesses of the silhouettes (if you don't get the jokes). Keep in mind this may be placeholding, or straight-up trolling. Also, they'll be more characters in the actual game. 28 seem so little.
??? (Tawny the Tiger? Neko Captain Cold?)
Wonder Woman
Jonah Hex
Doctor Fate
Firestorm
Green Arrow
The Joker
Sinestro
Robin (Damian Wayne)
Harley Quinn
Swamp Thing
Braniac
Cyborg
Booster Gold
The Question
Darkseid
Blue Beetle
Bizarro
The Flash
John Constantine
Green Lantern
Deathstroke.