Moss-painting
this was a form of art which developed on the planet Alderaan. It involved the cultivation of specific strains of moss which neither spread nor reproduced, keeping their position static within the artwork. The secrets of how to cultivate these mosses and grow them into a painting were well-guarded even on Alderaan, and were lost when the planet was destroyed by the first Death Star. Because of these secrets, moss-paintings could not be forged. In order to maintain the moss patches, speciallized moisture-control circuitry was developed to ensure the survival of the mosses.