GREAT idea for the hideous mirror in guest bathroom! add moulding trim with tile border around large bathroom mirror. Rather than removing large bathroom mirror, add moulding trim for a more refined look.
12+ Bathroom Mirror Ideas + 6 Tips for Finding the Perfect Bathroom Mirror
DIY Framed Mirror Tutorial~ Thick baseboard, and some corner round molding. cut a frame, after measuring the mirror. using 45 degree anglesattached the corner round to the edges of the frame with some wood gluecouple coats of semi-gloss white paint.
Framing bathroom mirrors - a great tutorial with step-by-step instructions & pictures. glue the molding right on to the mirror. I did this in my bathroom, not hard and a very inexpensive way to update a plain mirror.