Repetition - The use of the same visual element (usually a shape) multiple times. Repetition does not by definition indicate that there is any organization of the repeated elements -- at one extreme, the elements could be seemingly random in position; at the other extreme, the elements could be arranged in a very strict grid.
Repetition of rectangular shapes.
Unorganized repetition of organic shapes (water ripples and reflections).
By Pink Sherbet Photography from USA [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
Repetition of elliptical shapes with variations in size.
Monogrammist JHV (fl. 1650–1675) [Public domain], via Wikimedia Commons