The hard part is knowing what I should call the set done enough. At very least I need the transitions, water tiles for the underground section, and maybe a set of above ground buildings. The problem I have with the buildings is the temptation to add a second story, and they way lies madness as it would involve figuring out where to put stairs and if I want to do the upper stories on a separate tile or project them onto the same one. The first option would be flexible but you'd need to keep the two parts together somehow and the second option would mean cutting off a good section of every tile to do the second story as a projection. As is with the underground city I just figure if people want stairs between levels they can add some. and then the responsibility is on them to make things line up.