Might be too much of a good thing to have all that Walnut- how far apart are the two areas, and is there much natural light?
Something paler would look well on the floor, but I would chose something with a little variation in the colour (either a mottled colour porcelain tile, or something like marmoleum) as otherwise you will see every mark on it. I would probably try to get something that looks like stone, (but doesn't cost as much) and has a fleck in it to pick out the colour of the units.
For the splashback I am a big fan of neutral colours - if you get tired of tiles it is not a small job to change them, You can change the look by repainting your walls if necessary.
If you saw the state of my kitchen you might not take my advice, but there you have it!