A 15" x 48" painting I textured and painted in acrylics. I drilled out a small circle about the size of a nickel on the back of the wooden squares and circles (tiles). I applied polymer clay canes to the fronts and baked them. After they were cooled, I painted them and glued super magnets in them.
I hold the tile on the front of the canvas while I place the super magnet behind the canvas.
Above is a super magnet on the back of a smaller painting just to show you its placement. If you get tired of the magnetic polymer clay tiles on the canvas, you can turn your refrigerator into a piece of art.