This little mod was made by Hades85. It is not finished yet, but he gave his permission to use this file. I decided to upload it, because I saw he didn't do it himself, and some modders are interested, so here it is. I think it just lacks the imperial town center.
The mod just changes the colour of some buildings roofs from brown to dark blue, and gives a set of alternative castles. If you want to see pictures, just have a look on the topic: "alternative korean buildings" on the forums (mod discussion).
All credits go to Hades 85 and Sanghwi who created the original buildings.