Try a slim porcelain sheet in a concrete look finish. The large format size means you'll probably need only one, so there'll be no grout lines. Have a look here, at the Portland 3.0. I think the Kerlite range also does a concrete look and is larger, at 3m long. The other advantage of a porcelain tile over actual concrete, is that you just wipe it down. Concrete is porous and will stain.

We have tiles that do not have a gloss finish. They are Encaustic, or at least I think that is what the style is called.

I suppose the question is "What are you going to do with the untiled wall?". Will it just be painted plasterboard? If you do decide to just go with the 200mm tiled splashback you will need to be very careful with your tile selection with the sizing and how the edge of tile looks. You should probably select a 200mm tile, as you don't want a cut, half tile in the space between the window sill and benchtop. Some glazed, ceramic tiles also have messy edges, so make sure that your tile selection looks as good from the edge, not just the front, as you will be looking down on the top edge of the tile. Or allow for a tiling edge strip to conceal the edge, but these always make the space look visually busier. With so much happening in your kitchen with the open shelves etc, I would suggest a plainish, neutral tile and tile up to the ceiling for a cleaner, more streamlined look, that doesn't need maintenance and repainting in ten years time. Open shelves often look better against tiles. By tiling to the ceiling there is no exposed tile edge to look messy, which gives you a wider choice of tiles. Best of luck, Dr Retro of Dr Retro House Calls

Your kitchen is small and already quite busy. I would make it as simple and clean as possible. You can't beat ceramic tiles for cost, durability and ease of installation. Have a look at Johnson's Spectrum range to see if you can match the green. https://www.johnsontiles.com.au/product/spectrum/?utm_campaign=1602072422&utm_source=google&utm_medium=cpc&utm_content=304640004469&utm_term=&adgroupid=61761480198&gclid=CjwKCAjw_YPnBRBREiwAIP6TJ0idAicM8vfEevC-WrwRVNmbtUPHfDAjvNpkaOIo0hzN0dwMw9u1rxoC0VkQAvD_BwE You will get a neater finish with ceramic tiles than you will with trying to work with DIY stainless steel, particularly around the edges. There are lots of online resources to show how easy it is to lay smaller ceramic tiles. Leave the large format porcelain tiles to the professionals. Best of luck, Dr Retro of Dr Retro House Calls