Okay I did some quite big steps now and granted me a good amount of artistic freedom.
I defined the coastline more precisely and took reference from all the maps that we have from the game series.
I used the maps to define riverflows and also started to define baseheight of the land.
Here you can see this:
https://www.dropbox.com/s/gy19rgmuv9viep6/Sketch4.png?dl=0I decided to go with a topographic mapstyle at first for having a base to work with.
When the heights are done, I will go over to the terrain composition (mountains, hills, plains, farmlands, forests)
You are welcome to give me some feedback on this fourth sketch.