You can look through photos of these kitchen-granite-counters & see what you learn. I do not know if there is an exact rule (& innovative designers are always breaking rules), but I would not choose too many different finishes for a kitchen without professional help. One thought, if you're having different wall finishes (like the brick & marble above) I think ending at an inside corner looks best. http://www.houzz.com/kitchen-granite

Hi. It's hard to tell without seeing a photo of the space, but it would probably be just fine.

The backsplash looks like calcutta marble. We have that in our bathroom.

They were purchased new, but we had them custom powder coated at a local company that does metal painting.

They're a custom painted finish with a glaze. Where are you located? I might be able to suggest a manufacturer.

In Kitchener, Ontario
Are cabinets distressed? Having a hard time finding the right shade for cabinetry, how does someone come up with a custom colour?

how would I explain this finish to my kitchen company

I'm sorry for the delay - just saw this. They're from Brocade Home.

Actually that's called Mother of Pearl in our region, but here's a link to it as well. Thanks!
http://www.houzz.com/photos/111189/Madreperola-Quartzite-Polished-Slab-traditional-kitchen-countertops-other-metros

It's actually called Mother of Pearl here, but is also referred to by other names.

They're from Lyon Industries but we had them custom painted at a powdercoat paint company.