hi there! I've read somewhere that the best height for a wall sconce is the one that allows most of the people living in the house to enjoy the lighting from their normal positions without suffering glare from an exposed source (the bulb). So you can decide if that 66" would be from the socket or what. As long as all your family members, regardless of stature, get adequate task light. Here is a link that might be useful: bathroom lighting

I can't speak to much other than the polished nickel finish. We have Quoizel sconces in polished nickel that have held up well. They do have a glass shade and I'm hoping to get something a little softer for the new bathroom we are just starting to work on. This "French Cuff'" is lovely.

You could trim out the mirror like shown here, attach the sconces on the mirror and try decor on the vanity like shown. that's one way to decorate w/what you have. two mirrors, some type of tile on the wall (or a wallpaper) bring in a tall vase/stems for the middle decor accent. I'd also do a much larger area rug in front of the vanity. I like this one. look at the wood accents on the vanity. you need this w/all of your grya/white for some warmth. the vase/tall stems on a wood vanity tray. the gold sconces on the marble tiled wall behind the vanity. I mocked it up for you. I'd bring in some greenery w/a few hanging plants or orchids. or, bring in a trim carpenter and have him do something like this w/the mirror: or like this w/the sconces on the sides of trimmed out mirrors, nice lights right above taller mirror. I'd do a nice chandelier to reflect back Right now it's just a generic white vanity w/white/gray floor tile. amp up that wall w/peel and stick wallpaper. there are thousands of options (try wayfair or Home depot) At least you'd have something on that wall. or , tile is an option how about tile and some cool mirrors? you could do two taller mirrors, diff lights more ornate type of mirrors, diff llights taller mirrors w/some pendants, and vertical planks

A recent person on Houzz posted an update of their bathroom. I don't know how wide their sink is but it is right next to a wall, has a centered mirror, and sconces on the sides. Check it out .https://www.houzz.com/discussions/6348148/update-powder-room-no-backsplash-blue-walls-complete#n=240 Great that you can fit a 36" vanity in your bathroom. I have a small bathroom and that sounds huge to me!