There are plenty of ideas floating around online to give parents design techniques for decorating their kids' rooms. Wall painting or murals are popular choices, and those kids who are fans of surfing or the ocean may want to have crashing waves adorning their walls. Painting waves onto your own kid's walls is a relatively simple do-it-yourself project in which you're limited only by your imagination.
Remove everything from the walls in the child's bedroom. This includes posters, picture frames, mirrors, etc. Leave lighting fixtures on the wall, as they can be painted around. Move furniture away from the walls to the centre of the room and cover the flooring close to the walls with dust sheets to prevent accidentally dripping paint onto carpet or hardwood floors.
Hold a tape measure horizontally across the middle of one of the walls and lightly draw a straight line across the wall. This creates a visual guideline to follow so that your waves will be straight and not dip. Start on one side of the wall and use a paint roller to paint the wall a light shade of blue to simulate a sunny sky. Paint the other three walls in the same manner; allow ample time -- at least a full 24 hours -- for the paint to dry.
Hold the edge of the stencil flush to the end of one of the walls and the bottom flush to the line you drew (it should be visible through the light blue paint.) Tape the top of the stencil with painter's tape to hold it in place. Use a brush to paint over the stencil with dark to medium blue. Remove the stencil, place it next to the painted wave, tape it and paint another wave that is continuous with the first wave. Repeat to paint all waves onto the wall.
Paint all the walls and allow several hours for this paint to dry (you won't need a full day since you're not using the same amount of paint to paint the waves as you did the walls.) Fill a paint tray with white paint and use a sponge to blot white paint on the crests of the wave to give the impression of sea foam.
Most stencils come 36 inches by 20 inches, which makes handling the stencil easier. If you're stencil is larger and you find it unmanageable, try trimming the edges a bit with scissors.