I put a matte silver finish frame in my bath that has chrome fixtures and it looks very nice. It looks like this:

Perhaps you could go with a frameless mirror? or a dark wood color frame to match with your vanity.

I need to see your space . I often do a simple frosted trim around a mirror and no frame.

Maybe frameless with a beveled edge? Depending on what is in the rest of the room, maybe a rounded top or some other interesting shape other than plain rectangle.

Thanks for the suggestions! Here is what the bathroom is looking like so far! The medicine cabinet front still needs to be added (we are fixing a pain issue) — I’m considering something very plain - no bevel with a j-channel around it. Space between the the light and vanity is 38.5 inches - width is 24 3/4 on the backsplash.

What dimensions do you recommend and what placement ?

Already have a medicine cabinet - it has been installed (to the right of the sink) - just need to add the front of it when we finish painting :) Need a mirror!

Have you ever considered a classic pivot mirror? I had Minka Lavery pivot mirrors installed in in our smaller bathrooms and love them! Great quality. You can get them in all shapes (oblong, square and rectangle), finishes, and in various sizes.