I was cleaning in the basement when I leaned a full-length mirror against something. A short while later something got bumped and the mirror fell over and shattered, but didn't fall out of the frame. Looking at it I thought it would might be interesting to use it for a painting. I had planned to do a self-portrait anyway, so this was the first test.
I have to say, if you're thinking of painting something in a broken mirror, don't make it a self-portrait. It was extremely difficult to keep track of where I was in the mirror and on the painting. But overall, I think it's a pretty good effort.