I think that for most mirrors to be pleasing to the eye, they need to be about 2/3 of the width of the sideboard or buffet. And you want to hang it so that it is about 10" or so above the furniture, with the top of the mirror above most people's eye level, so just about any adult can check their hair or makeup. If you find a great mirror but it really isn't quite big enough, sometimes you can eke out the space with your lamps and other things, kind of making a mirror collage that gives the mirror the appearance of being the right size for the furniture. That takes a bit of experimenting with objects and can be a little hard to do if you don't have a good eye for it. I think you need a mirror close to 46" wide to work well with your 71" buffet. Try putting painter's tape on the wall above your buffet at about 46" wide and outline the shape of the mirror with the tape so you can get a feel for how big it needs to be. Les's mirror shot is great, you might take a look through some local antique stores to see if they have something similar..........AFTER you get your size down pat. Red

Thank God!! Someone finally suggested her picking what she likes...I read all of this and just groaned...I was looking to get a simple suggested ratio for horizontal picture to a stinking console. Now I have an idea and I saw a lot of things that I would give me zero joy...But then I like eclectic items. So it's all good...I truly think the real key here is to go with what makes you happy and what gives you joy. Someone else may not like it, but it's not their place... as soon as we quit worrying about what other people think about our decorating, then each person's personality will find that perfect mix... (Oh, remember, on your console, be sure you leave enough room so that one of your babies can curl up on the end nearesr a window or the front door to help be the official greeter ...like Wal*Bark??...Sorry, I don't know where that came from...)

2/3 the width is ideal, so approximately 48"

Use blue tape and make a mirror on that wall. Your eye will tell you which one is the correct one for your taste.