It's late at night here in Taipei, and having got back after several hours away from the house to find no more new votes have been cast since I left, I decided it was time to wrap up the poll since the result is, shall we say, startingly clear in its lack of ambiguity: out of a total of 103 votes, only 21 were for the one featuring blue ocean waves. Which makes the above the official cover for the third Dakota Merrick book, Empire of Light.
I got an email from my editor saying I should be getting a high-resolution image through from Tor at some point soon, and I'll put it up here when it arrives. Every email or tweet they received through their own linked page with the two covers were unanimously - unanimously - in favour of Cover 2. Thanks to everyone who took part. It'll be live in the bookshops some time next year.
Someone did ask in a comment who the artist was. I'm assuming it's probably the same person who did Stealing Light and Nova War, a chap by the name of Lee Gibbons. A bit of googling didn't turn up anything more informative than this page here, but I hadn't realised Lee had also done the covers for some of Ken MacLeod's books. If it's not Lee, I'll let you know.