Hello, jewelry is a very popular 3d printed item. You 3d model anything to be jewelry given you make sure to keep the wrist, necklace and ring sizes realistic. So your creations can actually fit and be worn. Keep in mind anything you are creating is going to be real and must support it self structurally. Also keep in mind how thick and thin parts of the design are. Use no more material than necessary. This will help to keep your designs affordable. As for rendering jewelry in Maya here are some links to helpful tutorials and tips.
Good tutorial showing how to render realistic metals:
Creating a metallic coin model in maya:
A modeling package specifically designed around making jewelry in Maya 2011:
Hope these help.