[img]http://i1.kym-cdn.com/photos/images/original/001/157/609/168.png[/img]

The mural in question.  Like Kronshi says, it's not clear if they're all planets or if some may be moons etc, but it's commonly thought by the sort of people who think about these things that the murals represent the planets that each Diamond was in control of.  

Pink Diamond apparently only ruled Earth.