Yes, a darker color or a subtle texture that would make the forests and mountains look more connected to themselves. Maybe even adding more trees and mountains in between the gaps. Right now they are individual pieces in close proximity to each other. Theres nothing wrong with that, because everyone that looks at it will understand where the forests and mountain ranges are. It just comes down to preference and the look you're going for. I prefer the connected look
some of your labels may look good with a small outer glow in a light tan color. it will help it to be more legible for the parts that cross over mountains, forests, and rivers.
Keep up the good work! its looking really good