There are many examples on houzz of contrasting counters for perimeter and island. For example butcher block on island and stone on perimeter or a solid color on one and something with movement on another. I would only mix two stones if one had movement and one was fairly solid. The stainless on perimeter and something else on island sounds good to me. Here is a pic of stainless counters with what looks like a stone breakfast bar. (I hope I understood your question right). http://houzz.com/photos/3137660

If you have bare walls, then choose colours that won't clash and would tie in wiht the room. Then pick out colours you actually like and pick a favourite. Most everything will go with Grey but contrast is usually more visually pleasing.

Your layout for you kitchen looks really good and would fit well with the mixture of black and white cabinetry. With the lament bench top, we would suggest melamine (entry level cabinetry) or acrylic bench top, which can come in high gloss feature or matt. The matt surface would go lovely with your choice of bench top, and acrylic is also a affordable cabinetry material. Below are some examples of how Reno4u has incorporated both black and white cabinetry together, without making it to dominantly dark. We feel as if these examples would be perfect for your layout, and depending on if you want more black cabinetry or white you can go either way. This design above is an example with more black than white, can be made matt or gloss with different handles/splash back and wallpaper. With a u shaped kitchen similar to yours, however from the pictures you provided your style may include different design below the island bench. Another kitchen designed by us which shows more white than black, with a bar built in which may suit your design better. We hope this helps you, please feel free to call us on 03 423 9067 and we can provide a free quote for materials and kitchen design, and help you finalise your design further. :)

I can understand your concerns about the gap between the end of the island and the wall. Although the new option is more practical, it's important to have a design that is visually pleasing as well. Have you considered centring the island to the back cabinetry? This could be a potential solution that would eliminate the gap and improve the overall aesthetic of the space.