For your tween, a bedroom is much more than just a place to sleep or study. It's a place to dream or connect, create or relax, so it's important that it reflects the personality of its occupant. When coming up with a design concept, be sure to consult tweens to find out what they want their bedrooms to look like.
Girls, especially, want to put their stamp on their space and are likely to have some strong opinions. It's good to set boundaries, but it's important to let your tween lead the way.