Cream! Match a tile to the lightest cream color in the granite. Then, do a light platinum grout.

I agree with Eld, you have a lot of gray going on and the cream would offer a nice contrast and brighten it up a bit. It will also be neutral so you can bring in any colors you want for accessories and/or fabrics.

Here's one that looks good to me.

Here's the one that Lars has linked to (the first pic) which looks like it might be a light travertine. The two below it are more options. I love the herringbone subway and to me it would work best with the style you seem to be aiming for. The one below looks like it's a tumbled marble and any one of these would be pretty.

What I wouldn't do is mix in a pattern. As you can see from the last picture. That is a really cool pattern and it would look awesome with a solid gray counter, but as is, IMO, it doesn't work because the pattern is competing too much with the granite.

I wouldn't be looking at travertine with the grey cabinets -- likely to be great with the granite but too much yellow with the cabinets. I like backsplashes that are light and reflect light in what can be a dark space. I would go white, but an off-white, not a bright white or look at a pastel grey or cream -- but it has to read right with the granite and the cabinets. Keep it simple -- single color and pattern so it doesn't fight the movement in your granite. Pretty much like the 2nd and 3rd photo lukkiirish posted. The tile in that last one is perfect with the cabinets. Just not the granite -- I agree on that one. It would be spectacular if the counter was more like the ones in the 2nd and 3rd photos.

light gray or cream., pull a color from your granite. i would use a very subtle pattern since your granite has lots of movement. the granite is the star, the BS a supporter. i would use matte finish since your granite and cabs have a sheen.

Is there another window in your kitchen? I like a well-lit kitchen and with the dark cabinets, I'd also go with a light color back splash. I'd take a small piece of your granite shopping and try to blend back splash tile with one of the lightest colors in the granite.

I would like a light colored glass tile

As others, recommend a white or very similar porcelain tile with a grout the same color, not a different color grout. That would not go well with you beautiful counter top.

My3dogs, there is a sliding glass door providing more light. Regarding the window. A new window will be installed which will have a white trim. I was thinking of running the backsplash tile up around the window. Will that be too much cream/white or is there an idea on how to trim out that area?

Will the new window be the same size as the current one? I ask because in order to chose a back splash tile, if you go with tile, you'll want to measure and see what size you'll be able to fit in the space above the window. It looks like you may have 3 - 4" above it now? Keep that in mind when you shop for tile.

I found a few pics online -I don't like the dark grout in the 2nd one at all. See how close to the ceiling, it points out any discrepancy in the level of the ceiling? Can you step back and take a pic so we can see both sides around the window? There may be a way to trim it out with wood or tile.

Find a really fun wallpaper..maybe black and white...loads cheaper than tile/stone. Most of them are really rather easy to keep tidy and when you get bored with it...change it!