Well as a WIP, what a start!!!
Now on to things that with some tweaking can look better. The highlights I feel is a bit over bloomed. I would suggest you do your highlight layer
below your line art, if possible. (I normally make a layer for my highlights, one I fill with a desaturated grey color that is smack dap in the middle of spectrum, color code: 808080. Put the layer on overlay. Then I use the dodge/burn tool on lower opacity to highlight and even burn for shadows)
(For a example result, check out the forests in my "Current Project" link in my signature.)
Definitely a good start for a map.