The spawn is a poorly built, seemingly unfinished wood+dirt structure with most furniture removed. It's main use is a storage unit at the second to top level.
I have all the NPC, all with different material house. The only one of my NPC not in the village is Dryad.
My Demonite Castle:
My first make of this castle was completely stone, then I decided to replace the stone with demonite ore. It shall not be changed, even though I'm not perfectly fine with the way it currently is.
Roger's Brick+Demonite House
He made a simple layered house, the first floor being brick, the second floor being demonite, the third floor being brick & so forth.
A small greenhouse used to farm blickroots. Not much.
Hocolo's Copper Castle:
I build it for him, to be honest. This castle is the reason I'm not completely happy with mine. The structure of his is much better.
A jungle inbetween two corruptions. What more could I want? This is where I farm Eater of Worlds. I also have a base in the jungle.
To the left:
A bit far to the left of the map is the dungeon. Nothing interesting until there. Further to the left are some meteor deposites & an ocean farm.