I recently framed the plain, builder-grade mirror in my master bathroom with a framing kit I bought from the mirror section at Lowes. It was super easy, cheap, and only took a half hour to do. They had light, medium and dark woodgrain colors to choose from and if you don't like any of them, they are paintable. You could use a light one and paint it out white, blue, red or whatever color fits your scheme. I'll try to post a pic but remember, mine is in an adult bathroom so you'll be looking at the overall look and structure, not the color.

I had someone make a frame for our mirror using fluted trim. I guess it's about 3" wide and instead of mitering the corners, I just used those corner rosette blocks. It looks pretty good. I have seen big mirrors such as yours with smaller frames (maybe about 24 x 30") mounted over each sink and that looked good, too. I have one word of caution if you do a painted frame and that is to make sure to paint the back of the frame black. I told the guy who built/installed my frame to be sure to do this so you couldn't see the wood on the back and he didn't listen. Sure enough, you can see the reflection of the back side.

I would switch sink and those cabinets moving them them to sides with drawer units in center. Yes, I have 12" drawers in my bathroom vanity now ... and the reality is that I have only about 8" of actual storage space. The hardware on each side of the drawer eats up so much of the space. Actually, I'd go with one 27" sink in the middle and a stack of 25-26" drawers on each side ... which would garner you about 21-22" of storage on each side of the sink. And you'd have more counter space. I would put one sconce in center I'd think twice about the double-bulb sconces. Remember that they're set against a mirror, so they're going to feel like FOUR light bulbs. Of course, if they're on a dimmer, you're in complete control. Also, drilling a mirror for a sconce's placement is tricky, and the builder will charge you for that risk. If you were to go with pendant lighting, you'd get the same function with an easier /less expensive install, and it's easy to have the light shine right at "face height". Admittedly, pendants are less traditional. No, no ... moving the drawers to the middle is a good idea, but only if you make them into ONE wide drawer. If they stay teeny drawers, you're still losing all that storage space to the necessary hardware. If you can add the extra recessed lights definitely do so. Be sure these lights are hooked to a different switch. That means you can use JUST the sconces OR both the recessed lights AND the sconces ... after all, sometimes you want to LIGHT UP the room so you can do your make-up or clean, but other times you just want a small, soft light to help you to the toilet at night. Separate switches, especially separate switches on dimmers, give you better control.

If the window glass is opaque enough to give you privacy, I'd leave it bare; I like the white wood trim. New hardware and lights, yes; plumbing fixtures and frameless shower enclosure if possible. You could get the width of the mirrors cut down by a good glass and mirror shop; it would require some additional sheet rock and paint repair for the newly exposed wall area but might cut down on the 'fun house mirror" effect of the sconce reflections if your lights sit outside the mirror. If you can put towels somewhere other than where the towel bar is on the original photo, a piece of art in that spot in primarily light colors could tie together the tile and gray walls. (Hard to tell the color of the tile - is it tan, peach, ???) Maybe you could find towels in the same color combo. Good luck!