You can grab a pair of pliers, stick both tips inside the keychain loop, and push it open, letting you add something other than a keychain or removing the loop altogether.
Another thing you can do is take a small Phillips screwdriver and open up the case to switch out the background paper (or flip it over).
Edit: if you get a Decoratchi kit/case, the gems and stickers that come with it stick better on a bare shell than the case.