Wow... Really, COOL idea.
But seriously, the tiles look really good. Very winter-y. I personally like the use of the ice blocks for frozen water.
The stairs that connect horizontally look great on their own, but when put together the top one looks off, and probably needs a special tile.
On the right side of the map, it's a straight line for the shoreline. Maybe make a small island covered with trees jutting out.
The bridge needs some snow on it.
All in all, I've seen almost no winter routes/cities at all. It looks really good, and is pretty unique for a hack.