A helpful little website entitled TV Size Matters gives you an idea of what your living room, basement, room, etc. would look like with whatever size TV you are thinking of purchasing. The website has a stock image of a livingroom with a couch and you can adjust the size of the TV hanging on the wall, giving you an idea of what it would look like.
One of the more unique things about this site is that it allows you to upload an image of your own room you plan on purchasing a TV for. This helps you get a great idea of where to put and what size TV to buy for your entertainment.