This is one side of the necklace, the side I usually have facing the world. I bought both charms and the chain at Hobby Lobby. They frequently put this line on sale for 50% off.
This is the other side. The only trick is finding a picture small enough. My solution is to take a picture of a picture I like with the flash turned off my camera. I don't fill the frame with the picture either. Then I order it from somewhere like Walmart or Sam's as a wallet size photo. Usually works.
So then I cut the picture to fit. Modge Podge it to the back. Then cover it in glaze. I like Diamond Glaze the best but have had a hard time finding it in Utah. Aleene's paper glaze works just about as well. I found it at Hobby Lobby too. I tried not to get it too thick or it takes days to dry. Slip it on the chain and add a charm and there you go!