Kids rooms are super fun to design, I use the below rules when decorating for kids:

If a paint color looks really light, stick with it. Nothing is worse than walking into a pepto bismol pink room
Throw a rug down, even if it's over carpet-it pulls the look together (and keeps your floors safe)
Let your child pick the bedding, you'll need: fitted sheet, flat sheet, pillow sham, pillow case, duvet, duvet cover & a quilt
Add photos-kids love pictures
Keep it simple. Don't worry too much about decor-it will be filled with toys in no time!