I know alot of people are looking for mushrooms houses like those in direwood forest. I think that is okay for a tier I or tier 2 house, but I think that a tier V or tier VI house could be like a dragon lair.
The large Palmyra trees, like the huge one in Bristugo, could be made with levels going upward in the trees interior, all carved wood with vine overgrowth and leaves scatter across the wood floors.
The only thing to watch for is that the footprint is large enough that you don't end up with lines of trees in certain areas, like the 25x25 plots.