In my opinion you can go with either bronze brown or silver gray go with what you love more

My choice will be Tumbled Classic Travertine Patterned or 3"x6".

You have many good choices, practically unlimited, I think. Another thing to consider is cleaning: do you prefer a smooth surface or a more textured or rough surface? A smooth back splash may be easier to clean. Some ideas --






http://tile-shop.com/products/koshi/koshi.html

Something like this would work quite nicely because it pulls in the brown tones and the gray tones. Installing it vertically would look nice, too, since the locations where it is going are very horizontal (i.e. you don't have one tall area) although that could be a bit trickier under the breakfast bar area.
http://www.lowes.com/pd_54637-87523-CHIGLAAR3013_0__?productId=3878787&Ntt=glass+tile&pl=1&currentURL=%3FNtt%3Dglass%2Btile&facetInfo=

http://www.lowes.com/pd_355248-74035-DG6858RANDHC1P_0__?productId=3477571&Ntt=glass+tile

Anything in this range of colors would look nice. I would just stay away from a square tile format - I think the linear look will work better for you. Also, I would keep it simple - just use the one tile. I think it will give you a very cohesive look.