Lookin' pretty awesome indeed

I only think the walls might be a bit short however;
it looks especially strange when compare the height of the building in the image below with the walls...

Instead of making the walls (visually) instantly stop at a certain height, you could sort of make them fade out using cell anims.
To create the fade-out effect you could either use a dittering effect or use multiple cell anims with a different translucency percentage. Although the last option would most likely take a bit more work to get right, it'd probably look best.