Stripes are easily created using painter's tape. Vertical stripes will tend to increase a sense of height; continuing them across the ceiling can create the feeling of a tent. Horizontal stripes are easy and versatile; consider painting a single wide stripe all the way around the room, or paint two or three bands of varying widths in tonal colors. You can hang artwork or photographs on top to make them function like a picture rail.
Stencils open up a wide range of possibilities for the walls. You can purchase them in shapes ranging from letters to to silhouettes of animals, boats or cars – or you can cut one from a piece of cardstock.
You can also use decorative painting as an accent, by painting a "frame" around artwork hung on the wall or around wood letters spelling out your child's name, for instance.
For murals with lots of detail, ready-made vinyl decals are a great option. These peel-and-stick graphics come in many different images, colors and sizes.