Neat map! Sketchbook Pro, hmm? I tried out the non-pro version when I first got my tablet... The dry media handling was really quite good, I thought, but the wet was not up to what I wanted to do and the software version I had was a little buggy with a rude tendency to die or freeze randomly. Lots of fun for scribbling, but the risk for loosing work made me not wish to attempt anything more. Anyhoo... Tangent

I agree with Midgardsormr's comments. The only other thing that gets me is the really heavy amount of black crosshatching with the relatively thin tool on your cast shadows. It doesn't really fit well with the beautiful bright color washes, in my opinion.

I usually try to stay clear of using black pigment for shadows as it tends to make things look dull or dirty. The crosshatching... for something like this, my preference would be to limit it to just a subtle texturing effect to add some interest for detail... using something like a colored pencil, if you'd like, in a shade darker or lighter than the wash tone OR go completely opposite in color for a complimentary kick! Which brings me to the last part... when you have a pretty big area to cover, usually (not in every case, it depends on style, but generally speaking) it's a good idea to use a larger brush size. In this case I'd vote for a watercolor type wash, as I think it'd look fabulous with the rest of what you've got going. Well, that's me anyway.