walnut color cabs...but not walnut? without knowing, are you going a bit modern? Take a look at Florida Tile website for example..[on our shower stall-been excellent]...and try a more new age approach-"Urbanite' in color concrete or "Soul" in passion antracite or "Horizon" in terra red for more warmth.On counters-you could do Wilsonart brune slate, deepstar flint or rustic slate-would pick up the more upscale mood of floor tile in my opinion. Tile is generally not a high cost floor-I wouldn't do bargain tile in a kitchen-get a good tile..and notch up the look..they even have tiles that mimic wood planks to consider. Daltile is another good tile.

I couldn't get your tild link to come up but I would say you certainly want to do something lighter than your counter tops. That would be too dark on the floor and based on what most walnut colored cabinet look like, I'd say yes you want to go lighter than that on the floor too so as to have some contrast. But you do not want to go too light (as I have white laminate flooring right now and nothing could be worse than a white floor). I'm sure you can find a nice medium beige tone that will work with both the cabinets, counter top and still accomadate a dark-ish grout color. Maybe something like this:

http://www.daltile.com/images/products/zoom/DG32_12x12_Russet.jpg
Or this:
http://www.daltile.com/images/products/zoom/DT_PT96_12x12_TmpBge.jpg

both from Daltile

Obviously, you will just have to take your two samples and look in person to see what exact tile keeps it all working together. There are so many choices though, I am sure you can find several that will work.

I cannot access the tile link. I would do something similar to the russet tones in youe countertop on the floor. Maybe a terracotta tile. That would really POP.

Here is a link that might be useful: morocco floor tile