I have no idea but it's beautiful. From the computer screen, they look like porcelain large format tiles with a matte finish. Try & Google that & see what you can find. I have a new built home & found large format tiles in a matte gray with a slight streak of white running though them. Found them easily at a local privately owned tile shop. Perhaps there is something similar but with that gorgeous pattern.

I found that they're from the 2015 VTwonen & Designfair and are a matte tile: https://vtwonentegels.nl/collectie/neo-decor-ambre-8/

https://www.vosgesparis.com/2015/10/vt-wonen-home-vtwonen-design-beurs-2015.html

These are similar in a matte porcelain but not as simple:
https://www.builddirect.com/p/Salerno-Porcelain-Tile-Urban-Concrete--15191951

I found them searching: gray deco tile.

Happy hunting! I hope you find something you like!

Thank you for your help. I like that but looking for something more simple. Thinking about using this one, which is a little more subtle.