This picture is not the greatest. I made a set of these magnets for my mom and my mother-in-law for Mother's day a few years ago. I got my instructions from Not Martha. I though it would be fun for the moms to have magnets that were pictures of all their kids/spouses and grandkids. They were really fun to make. If I was the kind of person who had magnets on their fridge I would make more for me.
To make them I measured the diameter of the marble and then used Photoshop to size down all of my photo. I put them all on one document and had them printed at Costco. The rest was about the same as Not Martha did.