Aside from performing design magic with little strips of wood, you can go crazy with paint.
Some might place windows in this position, but these folks have used paint. If you blow this up, you'll also notice the subtle diamond shape-within-a-shape.
Here are some artfully placed rectangles -- painted brown!
Here the paint is applied -- asymmetrically of course -- to the natural paneling of the door.
Hey, you can also do it with squares!
Boy howdy, can you!
Or you can just freak out and do a real painting.