I was looking for a way to temporarily display photos and be able to switch them out as the mood strikes. My plan was to have several hundred 4 x 6 prints made at a cheap place like Walmart so I could frequently change the display. I searched the internet and found a lot of suggestions but didn't care for any of them; they were either too cluttered with ribbons or alligator clips, didn't display enough pictures, were too expensive, or hid too much of the pictures. I then thought of using small rare-earth magnets - if only I could find some very small ones for a decent price. A quick check of eBay turned up 500 magnets for under thirty dollars, including shipping!
I used super glue to easily stick the magnets to some tempered hardboard cut to fit frames. I then spray painted the hardboard, magnets and all - first with gray primer and then with flat black. I had plenty of magnets, so I just used another one to stick to the front of each picture to hold it in place. To remove them, just pull it off with a short stack of magnets - it pops off easily. I plan to place stacks of pictures underneath the display so my kids and wife can change them out as they please. I think it came out nicely and meets all my objectives.