The darker parts of the map are really working for me. And I especially like the appearance of the northern ice field (North Pole?) and it's "edge". I find it to have a lot of appeal.
The southern dunes and the mountain peaks that approach white are a bit too bright, for me, to match up with the dark areas. If you darkened them up a bit, I think it might really work well.
I'm going to have to look up/revisit this tutorial as well!
Thank you for sharing.