Removing bathroom mirror from wall?

The mirror is off. It was secured to the wall with some double back tape & some kind of rock hard adhesive spread around. I was able to get if off with allot of heavy fishing line (that broke often). It took aver an hour getting through the adhesive. The wall behind it wasn't damaged by the fishing line, but the residual adhesive is impossible to get off. We're going to install a medicine chest there. Around the medicine chest in the areas with adhesive still showing, we're installing a new product that looks just like mosaic tiles but is actually peel and stick plastic. Anyone interested in looking into the tiles, http://www.thesmarttiles.com/

Thanks for the responses!!