The leftmost one is my favorite, although it does seem to lack a doorframe for some reason.
The center one would actually look quite good layered over a cliff, the flatness would be less noticable then, and it would look like part of the cliff. Alternatively, it could be edited to look like and underground passge, which would need to be flat.
The last "house", unfortunately, needs to be completely redone.
The roof is good, but he windows are awkward, the chimney is drawn from the wrong perspective, and the wall texture is questionable.
The pillar on the right also looks a bit flat, though that doesn't really matter, since pillars often are flat.
Overall good effort, but work on perspective.
