A great way to decorate a kid's room is with "clouds" - painted on the ceiling.  You don't need to be an artist to do a good job with this, just follow the procedure carefully.
Start with a base coat of a flat latex paint tinted to a powder blue.  Roll the paint on the ceiling in the normal ceiling painting way. Allow this paint to dry then proceed on to painting your clouds.
Clouds are painted on the ceiling with a flat white latex paint.  The cloud shapes are painted onto the ceiling with a sea sponge and / or a rag.  The key to doing a good job is to get wispy edges by thinly applying the paint out into the blue background.  Use a latex glaze with your white latex paint to give your clouds translucency. It is useful to have a picture or two of clouds on hand to kind of use for inspiration when painting your clouds.The clouds will have denser middle sections and more translucent edges with light, floating pieces of cloud that fade out into the blue background.  Make your clouds of different sizes and shapes and avoid repetition.  Above all, have fun - it's only paint.See Painting Faux Clouds for more details and see the Painting and Decorating Concourse for more information on faux painting techniques.