Silkscreens can be used on polymer clay, lay the screen on your project and add some good acrylic paint (such as Americana Acrylic paint from DecoArt) and spread it with a scraper, so that all the holes / openings in the silkscreen are provided with paint. Then you remove the silkscreen and the pattern of the silkscreen is now in the color of your chosen paint on the polymer clay. Super fun to combine clay colors and paint colors for surprising effects.
HappyThings has silkscreens from various designers / brands in the range, choice to .....