I used two tiles that were left over from tiling the shower. Turned them over and stuck some soft, sticky, padded foam bits (very technical term) that I bought from the $2 shop. I’ve had a huge pack of these foam bits and have used them all over the place; under cabinets, under tables and chairs.
I like the new coasters they look great against the rimu and also no more water marks on the vanity.
I may get over excited at some stage and even paint some pictures on the coasters but for now I'm happy with the white tile look.