if you can wear acrylic without feedback, you can glue/embed gems onto it. Also, silicone can be ordered in clear; it discolors much less than vinyl.
Westone briefly offered an option of adding textures to the face of it, which was really cool. I think people must not have done it much, because they don't seem to offer it anymore.
I get earplugs, and have them in all sorts of colors, including glitter, which I LOVE. Also love my dark blue acrylic, although I think a gemstone would be a good addition. Fingernail decals can be used on acrylic to make 'em fancy (on hearing aids, too).