See also op art and patterns/textures.
Contributed by Mucho
Contributed by Dafi Kühne
Contributed by Florian Hardwig
Contributed by Darius Kisielius
Contributed by Stephen Coles
Contributed by Anna Farkas
Contributed by Marianna Mooney
Contributed by Lluís Serra
Contributed by Johannes Stoll
Contributed by Joana Correia
Contributed by Rodrigo Saiani