Introduction
Just like in a landscape painting, background elements such as sky, clouds, and water seem to add atmosphere and depth to a scene. They help to provide both visual complexity and a sense that your players are interacting with merely a portion of a much larger dynamic environment.
Water can be used to supply natural-looking barriers to players roaming, while a well lit sky can be amazingly effective at boosting what would otherwise appear to be a simplistic and unnatural scene into an artistic force of emotional impact.