Find a photo of the desired landscape design using the Internet or computer illustrator program. Print the picture on transparency paper.
Paint the wall a base color. Off white paint works well and will cover up easy as you paint the landscape. Obtain paints in the colors on the printed image.
Set up an overhead projector in the room facing the main focal wall, such as the wall across from the door to the room. Place the transparency on the projector and increase the size of the image on the wall.
Trace the image of the picture on the wall with a pencil. Draw the lines of the photo in very light lines to make them easy to cover with paint. Turn off the projector.
Paint the image using 1-to 2-inch paintbrushes depending on the intricate lines in the design. Use wider brushes for large areas in singular colors.
Paint the remaining three walls in the room in a neutral color. For instance, for a seaside landscape theme, paint the walls in the same color you painted the sand in the mural.
Use stencils for accents on the other three walls. You can find these stencils at home improvement, paint supply and art stores.