You could look at cement tiles. They come in loads of colours, so perhaps you can find tiles with the same (or very similar) greenish grey, but just grey or black and white patterned ones would work too. Or even a different colour or a mix of patterns and colours.

I agree with Dual Designs that your colour scheme has a potential to look great, and I think dark(er) kitchens are here to stay for a good, good while. Copper adds a warmth and a textured softness of sorts (if metals can be soft, of course, be we are talking comparative feel of the space). I'd probably go for muted kind of navy(ish) or very dark (and also muted) green rather than slate OR black, but a very matte very dark slate might work the best. And yes, pick what will work for you and what you will love, unless you are planning to sell very soon.

* Just a note about this colour. * It is an extremely low Chroma (near neutral) paint colour from the Green-Yellow Hue Family. In balanced lighting, RAL 7047 will appear to be a lovely light to mid-tone, near neutral grey. In some situations you may get occasional moments of its inherent greenness. But it’s very important to test how it behaves in your space, for low Chroma colours from this Hue Family neighbourhood can shift positively blue in lighting, which spikes in blue/violet wavelengths. It isn’t blue and doesn’t have blue ‘undertones’. It’s an effect of lighting and context. It certainly doesn’t happen in every space, but you won’t know how it will sit for you unless you sample in your own situation. 🌈

Thank you 😊 I went for F&B skimming stone on three walls and Elephants breath on the long wall as I found ST was not warm enough to compliment the frame of the painting. On the opposite wall we have 3 windows and a double door so this is the largest expanse of wall in the room. I love it and think the two colours look gorgeous together.