Ahhh, thank you! Good eye. I'm not really sure, but it might be how the same-colored dunes blend together. I tried swapping for a different dune of the same color and moved it a bit.

Another scene using Spectrum Overlands, this time a desert community. Not sure if I should have stuck with one shade for the dunes?

Did another approach using Ricko's techniques. (Thank you!) Tried it where the waterline ended before the hills, so they had the sharper edges and edge effects. Then I redrew the water so the edges were under the hills. I rather like the softer effect of the water line. Thought about using the swamp trees but decided to stick with the palms (and a few conifers near the rocky peaks).

Oooo, I like that. I really appreciate the time you take to mentor me and others here.

This is excellent advice. I had a vague sense of the concept but having these numbers as a guide is very helpful.