Measure your mirror and create a circle that size in the design space to use as a template.  My mirror is 50mm

Create two more circles.  One will be larger than your mirror and the other just a little smaller so that it will frame it.

Move the inner circle to the front and Subtract from the outer circle.

Pick an image for your mirror and size it to fit into the template circle.  Set the frame to cut, the template to ignore, and the mirror image to engrave.

Use the 3mm basswood defaults to cut out your mirror frame.

To engrave the mirror I did 95 power 1000 speed 1 pass 200 lines.  I suggest putting a piece of wood under it so that it doesn't etch your base plate.

Test fit the mirror and frame to make sure that they line up.

Sand the frame a little to remove any burning on the edges.

Use an acrylic paint on the back of the mirror to fill in the engraved areas.  This color will show through to the front and make a decorative statement.

Stain or paint the frame.

Glue the mirror to the frame.  Be careful to keep the glue dots small so it doesn't get onto the displayable part of the mirror.

Use a command strip (cut it down to size if needed) to attach to the back and then hang in the dollhouse.

It adds a fun little statement and decoration to the house.