I like your idea of mosaic tile, and I think linear mosaic as opposed to squares would look best with the wavy, somewhat linear pattern of your countertop. Your window is in an awkward position, height-wise, but I would stop the tile at the bottom of the uppers, and then use Schleuter strip along the top in a dark silver to finish it off. Alternatively, if you go with subway tile, which I also like, you could use tile in a pencil strip, shown in pic 2, at the 12" mark up from the countertop (you wouldn't use it along the open area around sink) , so that it clears all your electrical outlets. For the area under the window, you would still use the pencil strip and stop the subway tile at that 18" mark (at bottom of uppers), then use Schleuter strip in a less striking (say, brushed nickel to match cabinet hardware) color to finish off the top row. I don't think tiling up around the window will look right, and it would draw attention to something that isn't your prettiest feature. That is absolutely stunning granite, by the way! In pic 3, I am just showing how pencil strip looks against a white background, and the effect in your kitchen would be similar. In the pic, though, the pencil strip is a bit lower.