For the time being, I've implemented only building houses and townhalls, but the framework for the other structures is done, so it will be a piece of cake (well, sort of) to add them.
Right now, I am focusing on writting some NPC code. Today I hope I will manage to implement a system where I define the type of NPCs (such as which clothes, genders, races, etc.) each type of NPC will be. For example, a blacksmith will wear different clothes than a barmaid, and will also look different.
So the idea is to implement the clothes and such in an xml like format, and when I add an NPC of a certain type, the server will know which clothes, genders, portraits, etc. to use.
I might also add some randomness, like multiple random choices for portraits, skin color, and so on, in order to avoid having all the NPCs look the same.