When you add a keyring to the cart, you can choose which images to use for the front and the back.
For example. Enter B6 and C3 to have two different swam images. Enter C7 and C7 to have the same kingfisher on both sides. If you order multiple quantities, then the same image will be used for all keyrings. If you want different pictures on multiple keyrings, then set the quantity to 1 but order multiple times.