The black and white pots contrast with each other not just because they're black and white, but also because of the different patterns.
The Annandale House by Greg Natale, in New South Wales, Australia. Photography courtesy of Greg Natale.
Tree Potting: Giant Bird of Paradise (Strelitzia Nicholai). Image from Adam Robinson Design's Casaba Waterloo White project
I've just found White/Black Or White/Grey Marbled Cement Mini Pot. Handmade and unique pots in white porcelain cement with marble pattern in either grey or black cement.
Mosman Landscape Design: Outdoor Establishments More - Outdoor shower, white pots