This is adapted from another tutorial I found which I couldn't make work, so I've made it easier.
I made these as Phantom of the Opera earrings but you can use whatever image you like. They make great sized, light earrings, perfect for presents
First, bend down the edges of the bottlecaps with a pair of strong pliers. You may be able to do without this step, but it helped me a lot!
Remove the plastic bits inside the bottlecaps. This can be easy or hard, depending on the type of bottlecap. I had two lots of them, one type which wouldn't come out no matter what, and another type which came out easily if pulled out with a craft knife or thin knife.
Flatten the bottlecaps! It's easiest to do this if you put it between two blocks of wood and hit them with a hammer. You can flip the bottlecaps over and move the wood around until they're as flat as you want them
Drill the holes! I can't tell you what kind of drill I used as I don't have a clue, but you'll know if it's small enough to go through but big enough to fit a jump ring through. You'll need to hold the bottlecap in the pliers again, over a block of wood and drill straight down through the rim
(I don't have a picture of me doing it with the bottlecaps, so just imagine that simcard is a bottlecap haha)
I found that the inside of a bottlecap is exactly 1", so you can either resize a picture on your computer using Photoshop, or look through magazines for an image the right size.
Cut it out using a craft knife or a pair of scissors
Use a strong glue to glue it onto the inside of the bottlecap, then go over it with a gloss varnish to keep it hard
Almost done! Now what you need to do on each earring is slip a 6mm jump ring through the hole and do it up again. Then open a 5mm jump ring to put through the 6mm one, and put an earring hook on that too.
Close the jump ring and you're done!