They're fake. I've seen those around one of the 3D art forums months ago, when the first confirmations of the series came out. Somehow, I doubt the original artist will be happy with what the site has done with his work.
Well, I have no idea how much those rumors can be trusted, but after months of working on a design for a new ship for this series, they're not going to say, "You know what, let's just do something that looks like Kirk's ship upside down. That'll be good enough."
