Jessica, Desilvering the mirror can be a simple as scratching off the
silvering on the back of the mirror. You can experiment with
different ways of doing it, from gently rubbing a spot with steel
wool to make it “diffuse” to using something like a scribe to scratch
hard edges, words, etc., into the silvering.
Something else you might want to consider is the “fun house” effects
you can get from convex, curved, and concave mirror surfaces.
Have fun - sounds like an interesting project.