Most children have powerful feelings about their current interests. Their hobbies and pastimes can make great bedroom themes. If you've used themes in interior design before, making the change may be as simple as applying a coat of paint, putting up a new wallpaper border and changing out the bedding and drapes. These days, there are so many themed home decorating products on the market that you can stick with one manufacturer's brand throughout if you want to. It's a foolproof solution that's fast and easy. One suggestion, though. Keep your major purchases generic. That bed in the shape of a car will have much less staying power than a standard bed paired with some car-related bed linens and posters.