You could have one side of galley kitchen cabinets in a richer shade of white (I'll have to start looking at the choices) and the opposite side in a grey. Will you have overheads too? Then the subway tiles in a softer shade of grey than the grey lower cabinets. I'd love to see photo of door handles.

Suggestions from neutral colours: https://www.dulux.com.au/colour/colour-trends/2018/essential Ceiling & walls the same colour is a good choice for square set. There will be subtle hue difference in various lighting situations anyway, which provides depth and makes for an interesting look.

This is a very personal choice as dreamer mentioned. You can order tile samples from tile cloud or TileMall for $15 for 5. Pick some options you like and put up in the kitchen next to the other elements. You will soon know which one you love the most 👍🏻

As said by big reader...leave white or paint the same colour, without the brushed finish, on the other walls. You can not bring another colour in. There is enough colour already with the orange wood and the bed cover. Also, the curtains look too small to pull right across your window correctly. They should be waved not flat when closed.