Within your country bounds, you can make some changes to it - mountains if you want/need them, changes to rivers, add in some lakes or even a big sea.
When I set it up I was working off Robbie's map, so the waters and elevation were to some degree already set.
But I was concerned with someone getting the landlocked areas. If you, or you and Chashio wanted to work out a large inland sea, that would be cool, especially as we don't seem to have any of them.