Very nice! I wish we had fountains or statues or hedges or something to spruce up courtyards a bit, mine always look like this too. Probably not really what you'd be focusing on in the zombie apocalypse, but it's fun to imagine.
Minor historical detail if you care: real-life crenelations are much higher. The idea is that you can step behind one of the taller ones and be fully protected from incoming fire while you reload your crossbow or whatever. I can understand leaving them short, though, because it completely wrecks the view from the tower and it's not like the zombies are shooting at
you yet.
...actually, come to think of it, since most zombies just run up and pound on the wall, higher crenelations make it *more* difficult to protect your castle, since you can't shoot down very well. So I guess if you want a more "realistic" look you go with the higher fortifications, or keep them low if you're actually defending in-game.