Wall decals are an instant way to produce a bold, detailed scene that captures his imagination. Peel-and-stick vinyl graphics won't harm your walls, and they peel off just as easily as they went on. You can find simple graphic shapes in solid colors, or ones that are made to look like custom hand-painted designs.
Stencils are another great way to bring a room's theme to life. They can be used to create a repeating motif on the wall for the look of custom wallpaper, or you can use larger ones to add interest to certain areas of the room – for instance, stenciling a row of cars along decorative molding.
Wall stencils are readily available at craft stores and come in a vast array of sizes and shapes; you can also create one that coordinates with the theme of your son's room using sturdy
Other painted effects are easy to achieve. Around a grouping of framed photos or artwork, you can paint a simple frame to showcase your mini gallery. Use a roller and painters' tape to paint bold vertical stripes in different tones of the same color, or paint a horizontal border around the perimeter of the room. Sponge-paint white clouds on a sky blue ceiling, or, if you have a steady hand, free-hand paint the alphabet over a picture rail or wainscoting.