I went with the same idea that a lot of people have done for magnets with the Clear pebble (The 1.5 inch ones), a magnet, and the scrapbook paper... but I used pictures in mine instead.
I cropped each picture to a 1.5 x 1.5 inch square on photoshop, then printed them all out to cut around the pebbles. This way I was able to the picture exactly how I wanted in sitting in the pebble, instead of too big or too small.
Then you paint a small amount of modge podge to the back of the pebble and place your picture on. Be careful not to get to much or too little. To much, your picture will slide and smudge... To little and you'll have air bubbles on your picture (Like the ones on Dallin's on the picture above). You will be able to feel it out. After they completely dry (Wait an hour or longer), hot glue a magnet on the back.
Sorry, I wasn't very good at taking step by step pictures, but you get the idea. :)
Super Easy, and my grandma's and mom's all loved them!