A render of The Ark posted anonymously in the comments of this website has led to speculation that the ancient Autobot ship could be the alt mode of Omega Supreme by an Italian Transformers website (translation). The validity of the render is unverified but it is missing the logos and copyright info that often accompany these types of leaks. While the image is pretty neat looking, it has to be taken with a grain of salt as it almost seems like a merge of two different images. I doubt the Ark has an alt mode and its part in the movie will mostly be the extent it is used in the moon landing sequences. Still it is an intriguing idea.
Update: To no surprise, the art is not Transformers related. As pointed out in the comments, it seems the design is from this website which has more images of similar design that are not Transformers related. Worth checking out just because the person's art is pretty radical but neat looking.