Dudley O'Shaughnessy, to me, is a perfect chose to play Aqualad. He has the look and he can totally rock the Blond hair. Also he's super sexy ;]!
I think Nicholas Hoult could play Robin, he also has the same bone structure as Robin and seems like he could pull off Robin's confidence.
Bonnie is a really good actress, she played Ginny Weasley in Harry Potter. I feel like she could play M'gann and she has similar features as M'gann too.
He most known for being in the Twilight films but I think Xavier Samuels could make a great Kid Flash. All he has to do is just dye his hair red.
Josh Hutcherson has been acting for a while now and he's mostly done roles were his character has an attitude problem, so I'm sure he can do Superboy/Conner some justice. Plus he's cute :).
Not just anyone can act like Artemis, who can play being strong but insecure at the same time,that's why I pick Blake Lively, who's in Gossip Girl, as the actress who could be Artemis.