Honestly I think all those agriculture fields you have in that grid look fantastic, I'd probably avoid the empty one though since it lacks the same visual mass as the others. I think the plateau line looks great, fits with the mountain lines and therefore seems to be keeping in style with your terrain forms. I think doing something thiner might look odd. The dashed lines for the rocky desert also read very well to me. Keep in mind the darker you make something the wetter it will look (relative to surroundings). I think this whole map is coming out really great!