After This:
https://www.robalexander.com/index.php/product/vault-of-whispers-canvas/
Things I see: Simple analogous color scheme. The green and white "hot spots" aren't really grouped. I thought they were at first but they exist as decorative notes that lead my eye in a circle. The grass hass greens but those are pushed really blue and with the rocks your eye pushes back out into the tower at the center. The focus is front and center but the brightest highlight is the moon which stands alone to the left third zone and helps keep the composition from being too dull. I think the way shadow and cutaway is used on the tower in the center helps create balance between lights and darks and a bit of movement. Also the cutaway gives an area you can stop to examine.
I clearly have a lot to learn here.