At first I thought it would be easy to make an image like this, but the more I wanted to detail, the more nodes were necessary, and they all interfere with eachother. So, I got lost sometimes, and wanted no distraction to figure out how to get something done without losing something else. It could well be done simpler, but, hey, it grew this way...
Btw. Bobby, with layers I mean 'physical' layers, like a lake and a planet. This is all one planet, but yes, with quite some surfaces. The blue nodes are just add and subtract or multiply blues to combine masks, nothing difficult.
The main shapes are drawn maps. I've been thinking to do this by subtle erosion, but then I'd need to paint a heightfield first (0-6m max). I might still try that, just to learn.
Yes, purples and lighter grey-greens are certain (flowering) plant species.