Batman: Plenty to choose from so it doesn't matter. Superman: Clark Kent costume for the lulz. Future Superman's black and white costume. Wonder Woman: Birthday suit. Lol, slightly joking. Either her Earth 2 costume or her main book costume. Bonus points for Lynda Carter costume. Green Lantern: Any of the other earth lanterns. Preferably John Stewart if he isn't another character. Aquaman: Brave and the Bold. Make it happen. Harley Quinn: Classic costume. Maybe a little special something that references Poison Ivy. Cyborg:..I'm at a lost. Nightwing:See above. Solomon Grundy: He wants pants too. Flash: Can't really think of anything for him. Maybe Jay's costume or a Max Mercury costume. Shrink him down and I'd go with Impule. Green Arrow: Don't care, probably won't play as him. Deathstroke: Don't care, but he must be voiced by Ron Pearlman. Lex Luthor: They are probably going to use his Greed Ring costume. Captain Cold: Parka and Cold gun.
Bizarro Superman for Superman Reverse Flash for Flash Adam West Batman The other Green Lanterns for Green Lantern Classic Wonder Woman (she looks more like her modern costume from what I've seen, but I don't know) Hulk for Solomon Grundy (since it's Fred Tatasciore, and hey I can dream) Classic Superman (red undies)
Whichever lantern is included (I think they'd only use one, or they have to make their movesets different), they have plenty of other costumes from their temporary turns as members of other lantern corps, not to mention Hal and Kyle's time as Parallax
batman- any one of his alternate batsuits will do ( but the original blaclava and cargo pants look would be interesting) nightwing- either his suit with the actual bird symbols or maybe a "batman" suit for when he took the mantle over from bruce wondewomen- well im not really sure for this one. maybe her royal amazon look instead of the battle amazon look ???? Cyborg- not sure where to go with this one flash- the outline neon light /slight blur look for when he became in a permanent state of motion superman- the blur outfit from smallville (not for everyone but i like it) or maybe his older look with a more defined chin and the streak of grey hair Harley quin- havent seen the current look for her in game but if its closer to the original then i want her arkhum city look and vise versa grundy- dont care bout this one one more for batman his exoskeleton suit that he used when he got to old for just a normal suit