That's a gorgeous map. If you're going for a watercolour and pen feel, then you're almost there. The only additions/amendments I'd consider making is a very faint green fill on the land which gradients to transparent about where the mountains are (so it looks like watercolour wash) and using a calligraphic pen for the coast so it tapers in places (to keep the line consistent with the mountain lines where a calligraphic pen has been used).
If you've got a tablet, laying down a wash on a new layer should be easy.
For me this is definitely a 'less is more' style of map and compositionally I find it really pleasing - it's got a very Ukioye feel to it.