11. Contrasting Shape.

Any defined area suggests shape. By placing, and thus,
contrasting your light or dark subject against a plain and
simple, but of an opposite tone background, and using harsh and
flat front-lighting or a strong back-lighting, you can strengthen
its outline, and thus, emphasize the shape of your subjects. In fact the more contrast there is in an image, the better your subjects will be distinguished.

Also, arranged into a shape of an up side down U, a curving S, a
Z, a star, a triangle, a circle, as well as a spiral and other
shapes, your picture elements, combined together, could make for
a better compositional appearance. The photograph of the tourists looking at the ships (seen below) is a vivid example of how light plays a crucial role in contrast and shapes related to it.