Great class! This is the design I made after watching this. A little rough but the end result is something I'm proud of!
The following pictures are just the different layers kind of showing the progress (and also in a way proof that I made it)
I started with a gradient.
Then I used brushes to create clouds and water
I then added a far midground element.
And more mid ground elements.
And foreground which in this case is a cave.
After this I added some fog to separate distances a bit better and added some lighting behind the far mid ground. And of course... Birds!