Good point. There's some psychology to be thought about here. You need an element in the picture that is of a known scale. The couch is pretty good, but maybe

Good point. There's some psychology to be thought about here. You need an element in the picture that is of a known scale. The couch is pretty good, but maybe include something on the wall so you can compare the two... a door frame is the best I can think of, since they are pretty standardised.