Simple, but simple can be good. I really like the colors and the texture of the mote!

My only critiques are that the angle of the clouds makes this look like an ISO map-- like the mote look like it is floating at a 45 degree angle to the off-camera ground, rather than parallel to it (the players would slide off and plummet to their doom!). I would think a fake "depth of field" blur on some generic scenery overlaid with a flatter layer of semi-transparent clouds would give a stronger impression of a flying island. It would also give a better impression of height (depending on the size of the scenery beneath) and induce a nice sense of vertigo!