Here are some cool Maxwell renders.
http://henriquelana.spaces.live.com/
Henrique is a an instructor at an Brazilian university. Some of these were downloaded from PaulKrush.com. That Maxwell put a ton of fire into the diamonds. They look real Henrique!

Here is site another from Ho Chi Minh City Vietnam::
http://www.jewelryrender.com/designing.html

3D Jewelry Renders