I remember a bath with those swag lights that had both of them swagged to one side, one higher than the other. Any chance that would work for you? You could then have them on the outside of the space further to the left a bit and it would give you more room. I think it would work with a larger square mirror, if that appeals to you. If the light on the left stayed close to where it is, but was up higher and the other light was hanging outside it, just a bit lower, maybe as low as they are now? And with not quite so much slack in the chain. Not one directly above the other, but one over more to the left a bit.

A bathroom needs a GFCI receptacle that is easily accessible by the vanity, but any additional receptacles in the room are optional. I usually use only one GFCI receptacle circuit, but always make sure there is one wall receptacle on the circuit near the entry door (for a vacuum cleaner, etc.). Based on the current popularity of fancy commodes (with bidet, etc.) I may start putting a receptacle near the commode. The counter height GFCI receptacle on the vanity side wall meets the basic requirement for a bathroom. I would probably just move the double GFCI receptacle on the long wall down to standard height and leave it there. That might also be a good location for a heated towel bar. Where to put the sconce is a combination of esthetics and electrical requirements. Most fixtures can be located as close an an inch from a side wall, but might look funny that close. You also need to work around the placement of the medicine cabinet and the swing of its door. The attached picture will give you an idea of what you might need to consider with sconce and medicine cabinet placement. If you look closely you will see that the medicine cabinets are slightly off from the sink bowl center, since that is the only easy way to make them fit with the three sconce lights. The placement of the sink bowls is determined by the vanity (cannot be changed), but lining up with that sink centerline would have cut into the space needed for sconces on each side. The sconces could not be moved farther out because they got too close to the window on the left and the wall on the right. Bruce

My mirror is roughly the size of yours. When planning my remodel, I used a 60" wall in my bedroom (the width of my vanity) but could have easily taped out a section of any wall. The blue, horizontal tape in the photo is counter height, and I hung my mirror there. I then cut out sconces in the rough size of some I liked and taped them up to see if I liked the dimensions. I did.

Thank you so much for these really helpful comments. @kandrewspa, Interesting suggestion about changing the sconces next to the mirrors, and I'll consider it although I do really love the ones I've got. Re the ceiling fixture, I do have one but unfortunately it is primarily an exhaust fan with just a small LED light, which I forgot to turn on when I took my photos. I need that fan, and there isn't room for an additional ceiling fixture. That's why I wanted to put in the lighting over the mirrors, to augment the sconces at the sides. I do already have both categories of lighting on dimmer switches; forgot to mention that. @JustMe, for up-facing sconces to go above the mirrors, do you mean something like this or this from Justice Design, or this one from Capital Lighting, or this one from Swiss Passport? Would you place them above each mirror, or between them?