I recently bought some metallic threads to use on my temari from Barb Seuss's on-line shop. They certainly add sparkle to a temari. A fun way to try all my new metallics was the first ball in Barb's book
Japanese Temari: A Colorful Spin on an Ancient Craft. (All of the temari in this post are based on patterns in that book, with my choice of colors. I am currently working my way through the book.)
Metallic thread used with the pine-needle stitch to fill empty spaces is fun and easy.