There are alternate Skins in Arkham City, allowing players to change the looks of Batman and Robin.

1970s Batman
AU: Preorder at EB Games
UK: Preorder at ShopTo
US: Preorder at Toys 'R' Us

Animated Series
AU: Preorder at JB HiFi
NZ: Preorder at MightyApe

Batman Beyond
AU: Preorder at Game
UK: Preorder at GameStop
NZ: Preorder at MightyApe

The Dark Knight Returns
Comes with the Collector's Edition of Arkham City

Earth One
AU: Preorder at JB HiFi
NZ: Preorder at MightyApe

Sinestro Corps Skin (PS3 Exclusive)
Buy a Copy of Green Lantern on Blu-ray from Best Buy.

Red Robin
UK: Preorder at GAME OR gamestation,
US: Preorder at Best Buy