Excuse me for a second, but I am distracted by the curtains in this image. I am all for creativity but those curtains are of dubious taste. What disturbs me most is that someone has gone to a lot of trouble to make them look like this. They could have used a simple sheer instead and it would have looked a lot less frightening.
What I was going to discuss for this tip was mounting heights of pictures. As is the case with this living room, people hang pictures too high on their walls. You rarely see pictures hung too low. My rule of thumb is to hang pictures so the centre of the image is at eye level when you are standing up.
Possibly the people who live in this house are extremely tall and have to duck to walk through doorways, but even if that was the case and the heights suited them, I would recommend lowering the hanging heights of all these pictures when they put their house up for sale. If in doubt, 1650mm is a good centre point height.
What you hang on your walls is important too and I will discuss this in a later tip. For now though, please remember that quantity does does not equal quality.