The choice of color for a kid's bathroom can be difficult. Although many designers recommend a neutral base with a white bathroom tiles and have, you might be able to renovate raised slightly when children grow up, the bathrooms are decorated with light colors and themes very much fun for children.
Here are some idea for kids bathroom decoration that you can use as reference :
Disney and Mickey Mous kids bathroom design
Finding Nemo Theme kids bathroom design
Here is a bathroom that is suited for twins: