You have to keep these things in mind, it is after all a space owned by your child. A playroom is a space where your child can play, and be himself. There will be no restrictions and no boundaries determining his/her behavior her. This is one room in the house that can always look messy and still look better.
How Can You Decorate a Playroom
If your child wants a particular color, so be it. The paint you use should be washable as more than often there would be characters and sketches drawn on them. If you don't have much time, you can go with the traditional blue for boys and pink for girls.
Make sure the furniture does not have sharp edges that might hurt, and are of a height that is comfortable for your child. The furniture has to be kept to a minimum providing more open space so the children can make use of this space in any way they want. Too much of furniture would clutter the room and eventually there would be no place to play.
Don't keep toys that are repetitive, and don't keep toys that require parental supervision. There should be sufficient toys to keep the child busy, but not so many as to crowd the room. Also include a few toys that would help in the education and growth of the child.
You can also ask your little one to decorate these boxes according to his/her choice. Always keep a wind chime for some beautiful sounds and some other objects that might appear fascinating but not harmful to your child.
This might take some time to complete, but imagine how happy your little one would be. If he/she doesn't have a particular theme in mind, you can choose from famous themes such as Lion king, Jungle Book, or any of the Disney characters.
Surprise your child with a playroom that is above his/her expectations, and see how happy it makes you as well. Hope the playroom turns out better than you ever thought it would. Best of Luck!