But in my question I was wondering about interior finishes in homes other than plain plaster.
Here's some to ponder:
Notice on that last one the curious tiled object. It is a Kachelofen, a tile oven. The procedure of using these is to get them very hot on the inside in the morning, and the thermal mass of the whole unit will slowly diffuse the heat during the day. Supposedly they can heat an entire house for a day with just a small handful of wood.