I've added glitter, loose tea, coffee, sand, and tiny pieces of grated baked polymer clay to some of my pieces. You can get some really interesting looks by including other powders or dried organic material to your clay.
This necklace from Amazing Designs
opal can be recreated in polymer clay, as evidenced by these Pinkish Purple Opal like Cabochons from Art Makers World
This Spring Leaf Window Pendant and Earring Set from TTE Designs
uses embossing powders in its design.
is fashioned from polymer clay that has a few glittery gold inclusions.
The use of inclusions in your polymer clay creations can enhance the look you're going for. I urge that you give it a try and you'll be surprisingly pleased at the results.