What happens next?

How to create a ninja bedroom
Go natural!
Natural light, earthy tones, and natural materials like wood are all applicable to zen principles. This creates a cohesive look to your room and sets the tone for the rest of your decorating to be influenced by japanese, martial arts, and ninja decor.
Take time to declutter and get rid of knickknacks.
Simplicity is key in the art of zen. Not to mention, ninjas don't have personal affects.