The mirrors in our bathrooms are the plain ones just glued to the wall. Using scavenged trim from the construction of our house, my husband cut two frames to fit the mirrors in our master bath and kids' bathroom.
Here are the before and after shots.
We used double-sided adhesive to adhere the trim to the edges of the mirrors. My sister used a Liquid Nails product designed for use with mirrors.
What a quick and easy transformation! You gotta love a man with a miter saw.