I adhered a faux wood contact paper on the back of the mirror, then spraypainted the contact paper white. The reason I used the faux wood style because it seemed slightly more durable than just the white contact paper, particularly at tight turns and corners or points.
I adhered the contact paper to the back of the mirror. You can also put the contact paper on the front of the mirror, but if you have a lot of little lines, all these lines will show up as a double image when you look at the mirror. So, I put the design on the back of the mirror to avoid this doubling effect. If you do this, you will have to sandblast a little longer than if you’re doing an image on the front. The sand has to cut through the reflective surface on the back of the mirror. I like the lack of double lines better, though.
The paper held up well under the sandblaster and gave me the nice corners and points I wanted.