Designating Jewelry Size in Photos

I'm trying to come up with a way that someone shopping for jewelry on the internet can visualize the size of jewelry.  In the example above I made a cardboard - life size ear "manekin". I added the ruler so that both inches and cm are displayed.  This is a mockup and I wish I could find a really nice display manekin that would incorporate these elements.  Most of the ones I've found are great in a store but deceptive in photography.  The ideal of course is a live model - not always easily available.  Plus people come in all sizes and even showing jewelry on a model does not always truly represent how it would look on someone of a different size.   I welcome suggestions or ideas to help solve this problem.