If you do 4 sconces, 2 for each mirror, it will make each mirror seem its own entity, IMHO. If you do a double sconce in the middle, it seems like.....an after thought? And the sconces will not be equidistant from each other and the mirror. My OCD kicking in, I suppose. If the space between is larger than the mirrors, I think you should go with 2 separate sconces. If the space is smaller than the mirrors, I think you could go with a double light. Just make sure the spaces are fairly equidistant.

Thanks, Chispa. The ceiling fan was installed this week, so I can finally see in the bathroom. Here are pictures taken without flash. The black walls make it look darker, but when the drywall goes up, that will help. The floors, walls, shower tile, etc. will be light colored. Plus the shower is essentially open with two walls of glass. The toilet will be on the left corner where the towel is on the floor. The tub will go on the lower left where the missing tiles are. The two yellow circles represent where the lights will go above the vanity. There is not much room since the vanity is 48" wide. I could move the vanity to the wall on the right, but I believe the lights would not be bright enough to reach the door. If I put two lights with 100 watt bulbs on the toilet wall, the lights should reach the door. I guess I could put a double light on each side of the mirror, but I have not seen any pictures of double lights on each side of a mirror. The first is 18" wide and the second is 12" wide. That takes away space for the mirror which I need to reflect light. I would rather have a 36" mirror than a 24" mirror. It looks like a single light on each side of the mirror will have to do.

For this type of installation, I think you're better off having a custom mirror made by a local glass contractor. You'll have to have the sconce j-boxes installed prior to the glass guy doing an onsite measure, then they can make cut-outs for the j-boxes. If you like, you can have your contractor's finish carpenter make a frame for you to install after the glass goes in. And no, it's not a dated look. I'm doing this for two new bathrooms in the same home as we speak.

Well, I am trying to make similar decisions on this myself. I too had come across that it is better to have sink lighting from the side rather than above but have found the layout to be challenging and busy. So, I checked houses for sale with 2500 - 3500 square feet and none of them had side sconces around their mirrors. And only one or two had frames around their bathroom mirrors. Most of them had one large mirror across the sink area with lights over it. A bathroom can be a busy area, so from a minimalist standpoint, no frame. Now a mirror in the Livingroom really needs a frame.