I found white wooden frames at Walmart for $3.00 a piece and took the glass out. The I framed 8x10 pieces of sheet metal that the hubby cut for me. (You can get a pretty decent sized sheet at the Home Depot for around $6.00. It covered all of these and a previous 16x20 project.)
Made the magnets with stickers and scrapbook paper that I already had. I like to buy my "pebbles" at Target because they always have the larger size in stock and you can get a nice big bag for around $5.00. I buy my magnets in sets of 50 at Walmart where they are more affordable then even my local craft stores.