I worked with a japanese like map time ago, is not the same style, but i have some information when i was studing to do one, wut costed 3 pages of forum if want to take a look, it started here: http://www.cartographersguild.com/ge...agacea-20.html

One thing that i guess that you need to work is try give a vertical and standing felling. Dunno right, maybe coz Japan have this format or the habit using flags or same dor kanjis. Looks like a flat shape does not fit right with japanese, but i beleieve cool for something as China based.
Btw, the aqua brushes give a nice japanese painting that i really liked.
Maybe smooth borders will be nice too.