I agree with palimpsest - choose mirrors that are the same size as the vanities if they are the same size. Use the space around it for lights perhaps (sconces,) towel rings, makeup mirror, art or the like! With that angled cabinet you have a beautiful feature wall that could have gorgeous art and really be a knockout!

Great idea to mock it up. Unfortunately, the vanity isn't in yet - just a blank wall so far but it would give me a good idea of function - even without the vanity. I'll see if I can find something to mock it up with. Living in temporary digs so nothing is ever just at hand. And I do have to let him know early tomorrow. I wonder if I get it a bit smaller, if a frame shop couldn't frame it for me so I could hang it rather than glue it? That would mean I could pick whatever I wanted for a frame rather than finding the "right" one at a store. I did google images of round mirrors over vanities and many do seem to just be glued to the wall - which i thought would be weird until I saw the pics.

Fibonacci has the answer. Oops, just noticed you said you'd like a round mirror.

Thank you so much for your help! We actually do need the tower for storage as the bathroom is not very big at all. It currently has a bulky built in linen closet on the left hand side of the vanity and the current vanity is even smaller (60") that my husband and I have shared for 10 years. So while I'd LOVE more counter space, even the extra 9" we are gaining feels like a lot for us. We put the tower on the right because it is next to the wall when you walk in the door which keeps it from being in the middle of the room breaking it up. It helps that the top part of the tower sets back on top about 6" from the facing of the lower cabinets to make it feel less intrusive. I am concerned that a 3-light fixture may make it feel more congested, but I just don't know as it seems there would be room for it.. Is more light better or would a 2-light be better for scale? I do love symmetry, and you have no idea how much it pains me to not have a perfectly symmetrical vanity.. But it really is the best option for the space due to how tight the bathroom is as a whole. The tub is directly in front of the vanity (about 4.5' walking space) which also sits in front of a window providing a lot of natural light in the room.