Batman Arkham Knight contains a variety of Costumes that Batman can equip in his adventures throughout the game. Certain suits are obtained by playing and completing the Main Story, while other costumes can be obtained via DLC, or console and retailer specific preorders.
To Equip these Costumes, access the Showcase gallery from the games main menu and select the desired skin and choose “set active.”
The Batman Beyond skin is based off the animated series taking place after the events of Batman The Animated Series, but has a Rocksteady flair to the design. It was initially available to PC users bundled with the Dark Knight Returns Skin, and is now available seperatley as DLC.