It takes a bold individual to paint their walls black. Most people tend to shy away from darker walls -- and for good reason. Striking the right balance between dark and light can be difficult, and not all spaces can support this design move.
If you are considering going dark the first thing to evaluate is the amount of natural light the room receives. If it's low on natural light, dark walls are a risky idea. High ceilings are an added bonus, and will prevent the darker walls from making the room look squat. Gray and black are great for accent walls, and for highlighting collections or framed artwork.