Now, you would want to make your terrain seem like it has a bit more depth, this is easily done by making the map larger, and adding mountains in back of the mountains, several layers also, if you think it necessary. The fog seems nice as of now, but not by far realistic, I believe light blue or light grey would suit better, but thats your choice.
For now you should focus on details, adding more to the actual terrain, and making it seem like it have more depth.