I don't know who any of these characters are
(well obviously Batty himself and Penguin)
There's only two others you might have recognised.
The guy in the white suit and skull mask is Black Mask aka Roman Sionis. Former rich kid and friend of young Bruce Wayne who becomes a major crime lord. He wears a mask made from the wood of his dads coffin, and following a fire it ends up fused to his face. Joker was hanging out in his factory in Arkham City, and there were a lot of references to Black Mask being the only person to escape from Arkham City.
The guy in the funky armour and two tone mask is Deathstroke aka Slade Wilson. Worlds greatest assassin, expert with all known weapons and one of the few people to ever beat Batman hand to hand (he took out the whole JLA at one point as well) He's got some weird explanation in the comics about using 100% of his brain whilst everyone else only uses 10%, but basically he's really smart, really fast and really dangerous. And Aoife apparently has a crush on him. (as a weird side note he was created by the same person and at the same time as Deadpool aka W
ade Wilson, and originally they had almost identical costumes. Is it any wonder Marvel and DC spend a big chunk of time trying to sue each other for copywrite infringement?)