any kind of undecorated mirror, preferably with a wooden frame
scrap pieces of pretty cloth, buttons, beads, coins, silk flowers, ribbon, etc- the choices are endless
What to do:
Cover your work surface with a piece of newspaper so glue doesn't get all over.
Spread a layer of glue on one part of the mirror at a time. Stick on your decorations. You can overlap them or keep them separate. Don't worry about getting glue on the glass, it can be scraped off after it dries.
When you're done decorating, let the glue dry (it will become clear) before hanging the mirror.