Marble, as a material and pattern, has had a real resurgence of late. It has become the kitchen splash back of choice and its infinite permutations can be found across the fields of graphic and fashion design. Pop on your favourite Pucci dress and peruse this selection of colourful swirls.
A little project by Lightning & Kinglyface which will make you want to swirl ink around a petri dish of milk. If that is what they used. One of those things you could look at all day.
The University of Washington has an extensive collection of patterned papers, most of which are marble based. You can see them all here.
Aside from the rock itself there isn’t a great choice of marble in the natural world. Mould just about ticks that box, especially woven through cheese. Here is some cheese set against marble backdrops by art collective Ptohograhpies.
Finally, some photos of actual marbles by James Day. Almost like candy, a lot like mini planets.