What are the benchtops going to be?

Perhaps you could follow MB's advice and match the sofa colour for the splashback, then introduce the teal blue with accessories. I like the following images showing those tones together. You would need some more wood items to add warmth to the glossy white kitchen though. Do you have a picture of your sofa handy?

I am making very similar decisions and am thinking of going for a monochrome graphic pattern like the examples you have. No doubt it will date, like everything does, but at least I will be able to change the look of the kichen by changing the colour of less permanent accessories. Gallifrey, I am looking at doing my kitchen in a very similar style and colour palette as yours, could you tell me what the finishes on your cupboards and benchtop are?

It really depends on your personal preference. I personally think that a splash back that is different to the marble island would be suitable! Have you thought about frosted glass or even a tinted mirror splash back? They do add value and can also be a great focal point in any kitchen. :-)