i dont think this has anything to do with logos but this is pretty sweet! minimalist fairy tale posters Menos es mas en diseño es todo y contar mucho con muy poco es la magia y poder de comunicación del diseño gráfico.
"Rubin Vase. This is one of the most famous optical illusions that exists. There are two things that you can see in this image ... In black you can see two faces looking directly at one another. In white, you can see an interesting curved vase."