While the PF downtime buildings all have descriptions and defined builds, they can be reskinned. So long as the building serves the same purpose, and doesn't change the returns or benefits - you can reskin just about anything. Here are a few examples:-

Tenement - The basic function of a tenement is to provide cheap housing for up to forty low-level NPCs, who will generally be L1 commoners. In the country, this might be a row of Long Huts (Think one long room, with sleeping lofts at each end), that can hold an extended, multi-generation family. In a town, where space is at a premium, it might be a block of eight rooms that can each house five people. I know it sounds mean by modern standards - but that is actually how many common people have lived historically - and matches up with the PF Cost of Living levels.

Farm - This represents a small holding or market garden type farm - but crops and animals will change according to the environment. A hill farm might have a small flock of sheep, a lowland farm might cultivate three small fields of vegetables, a Mediterranean farm might concentrate on olives and figs.