Big and/or bold art: By virtue of its size and function, the bed is clearly the focal point of a bedroom, and over-sized or brightly colored art will immediately draw the eye there.
Headboards: Headboards are an obvious answer, but they really can set the whole tone for a bedroom.
Work with windows: With colorful curtains, windows can act as a substitute headboard. On the other hand, sheers let the sun in for all your plants.
Walls that talk: Be it a bold color or something textural, focusing on the walls can have just as much of an impact as picking perfect artwork.
Go low-key: If any room should be peaceful, it should be the one where you snooze.