Hello! Solid surfaces and stones are used for backsplash all the time. You should have no problem doing it for your island backsplash. Cambria provides great customer support so if you have any questions or are concerned about your installer's skills, just give them a call, and they'll be more than happy to walk you through the process. As far as the thickness for vertical surfaces, I believe it's 3/4". I hope this is helpful! Rena