Some prefer to balance the page. It is seen longer. Elements that are DARK carry more optical weight than element that are light. Color conveys more optical weight than black and white. We realize that color is not a luxury all can afford but good balanced layout is a adequate substitute and you can achieve a lot with black and white.
White space is essential.
It can also be in any color. It becomes a spotlight. Rectangles are usual shapes. Everything else conveys optical weight. This means squares,triangles, ovals, circles, elliptical shapes, cubes, and others all convey optical weight.