Are you using side sconces or overhead lights? Is the vanity in an alcove? I would only use a mirror centered over the sink if you're using sconces. Just about anything goes in that case. My favorite look for a full-width mirror over a longer vanity is a narrow one that's raised a few inches above the backsplash. This could be used with either overhead lighting or sconces mounted to the mirror. Your glass company would cut holes for mounting.

Appreciate your reply tartanmeup! I agree about overhead lighting and shadow. - If I were to mount sconces on both side of a mirror and the mounting plate is 4", on top of 4", how much more space away from the wall would this mirror need to be? - I want to have one long mirror, would 2 sconces, 1 on each side be enough for this span? don't really want to go through the mirror for the 3rd sconce in the middle. I don't think mounting through the mirror is in keeping with a modern/minimalism that I'm going for. - If I go with pendants I would try to get them down to my height to avoid shadows. My vanity is 24" deep and maybe mounting this 8-9" away from the mirror down to my height wouldn't get in the way. Would pendants be considered modern/minimalism? I think if I go for pendants, I would use these. I think I have ruled out all the pendants above. At lease this one won't direct the light downward.

Geez Louise, I'm back nearly 3 months later, still pondering this--yikes. Until now, I'd planned to cover most of the vanity wall in a plain wall mirror. But now that my GC covered the entire wall (!) in Porcelanosa Madagascar Blanco tile, I almost hate to cover it up! So now thinking of doing a pared-down single mirror or a pair of mirrors (something I was not keen on previously). But proportion seems a foreign language to me. I cannot figure out what size or shape mirror would look right in this space. Help? FWIW, the floating vanity (which will have clear-coated walnut drawer fronts) is 56" wide and is mounted 36" above floor. The Porcelanosa tile tops out at 7 feet and there's a sloped ceiling above. That giant light switch box is even more annoying in person, yeesh.

Bigger is better as you're realizing. The console can be as wide as 75% of the space between the blue tape and the bedroom door. Then the mirror can be as wide as 75% of the console's length and should hang 5" above it. Does that help? Don't forget a striking area rug and light fixture! Do you still have matching paint to use on the vent above so it fades into the wall?