I realized I never posted the details of how I do my slate tile coasters, so I will share the steps here.
Putting a coat of clear polyurethane will give that wet-look result. I put several coats on- at least three or four before I add any design. I let it dry overnight to cure.
Creative Bling. Her desing sare perfect for vinyl because you can get such detail you just can't with paper.
You can buy these tiles at the hardware stores usually in a little package. I think you get like 8 for less than $4.00. If you get the chance to hand pick through them. Pick ones that are smoother and less edgy and rough. The vinyl will adhere better. Minor roughness hasn't been a problem.