There are a number of DLC costumes in Batman Arkham Knight for Batman, Nightwing, Robin, etc.
How to Unlock Batman Arkham Knight Costumes
In order to change the costume, open up the Main Menu > Showcase and equip your desired costume. Moreover, note that your equipped costume will also appear in the cut-scenes.
Anime Batman Costume
To unlock this costume, you simply need to create a new WBPlay account and sign-in using your newly created account.
Batsuit v.7.43 Costume
This costume from Batman: Arkham City is automatically carried to Batman: Arkham Knight right from the beginning.
Batsuit v.8.03 Costume
You acquire this upgraded costume automatically as you progress through the game’s story.
Adam West Costume
This costume is a Playstation exclusive pre-order bonus. All Season Pass owners will receive the costume across any platform by Fall 2015.
Batman 1st Appearance Costume
This is another pre-order bonus available to players who pre-order the game through Amazon or have Batman: Arkham Knight – The Serious Edition.
The Dark Knight Returns Costume
You need to have Gotham’s Future skin pack on Steam in order to acquire this costume.
New 52 Costume
This is a free DLC costume which can be acquired across all platforms i.e. PC, Playstation 4, and Xbox One.
This is another DLC costume available to anyone who purchased the Premium Edition or the game’s Season Pass.
This is pretty much all we have on Batman Arkham Knight unlockable costumes. If you wish to know something else, make sure to let us know in the Comments Section below.