I used a technique I learned years ago. It is a resist technique which is called "Joseph's Coat."
You start with glossy white card stock and brayer it using a dye rainbow pad for your ink.
Next, take a solid image stamp (one you ink up rather than color in) and using Versamark or another clear embossing ink, stamp randomly all over your card stock. Then sprinkle with clear embossing powder and shake off the excess.
Then heat it with your heat gun until all the powder is melted.
Now using your brayer again, brayer over the entire surface with black dye ink.
Use a paper towel and go over the images to remove traces of the black ink on the embossing.
Cut your paper up to use as desired.
This makes a very bold and beautiful effect and is fun and easy.