I think the only thing missing for the buildings is a little "separation." They look like a single building rather than a chain of connected buildings. Maybe a little something to show where one building ends and the next begins would help? Kind of like what you did with the city walls, you can almost see how they are sectional. That might give the buildings a little more pop. I'm not really sure, though. I've never had much luck with cities/towns unless I drew them by hand. Other than that, things look fine to me except for a tree that seems to be growing out of the river.