Jose Guadelupe Posada (1851 - 1913) was a Mexican artist who were famous for his portrait of 'calaveras' - or skulls in Spanish. He used the medium of these human skulls as a device to criticise aspects of Mexican life, politically and socially. His main focuses were mortality of humans, bourgeois life and the dictatorship of Porfirio Diaz. His illustrated literature were widely popular with the lower classes of Mexico.
Years after his death, the public image of these calaveras became closely associated with El Dia de los Muertos. His representation of a dead figure (the skull) to resemble human life is greatly reminiscent to the concept of the holiday - that death is just a continuation of life and the calaveras may very well be used as a equivalent to a human living in the afterlife.