I recently added in stone walls and stone gates. These will probably end up being the 2nd or 3rd tier of walls since they are so massive. Right now they have a ton of hit points in anticipation of getting siege weapons working. Units cannot move through walls (though they can attack them), but players can move units through gates they own.
You will also notice a new building next to some of the crops. That is for the next update. I still need to work on the mountain tile graphics too.