Nothing at all
It is a ruffled tulip and Stephenie Meyer didn't have anything to do with creating this cover so on her website StephenieMeyer.com she states that even she doesn't know what it means.
Stephanie Meyer had an extreme connection with the Twilight cover, but the New Moon cover was just made to help catch attention. It was strictly for advertisement purposes. However, some say it is how Bella withered without her sun (Edward) helping her grow.
Yes and they all represent something
What do you mean the theme, I'm guessing what is the cover about it's about Bella from her human life up to her vampire life as on the checkerboard i believe a Queen as Stephanie Meyer put the cover as.
OOOOH! I KNOW! Ok so I got this of Stephanie Meyer's website. The cover shows a flower that's petal has come off. This means it's dying. This shows that Bella is dying without Edward.
The initials "L. M." in the author's name on the book cover are significant because they represent the author's identity and are used as a unique identifier to distinguish the author from others with similar names.
Stephenie Meyer or the publishers
Zephyr
See related links.
This is a quote from Stephanie Meyer's website. Here is how she describes it."Breaking Dawn's cover is a metaphor for Bella's progression throughout the entire saga. She began as the weakest (at least physically, when compared to vampires and werewolves) player on the board: the pawn. She ended as the strongest: the queen. In the end, it's Bella that brings about the win for the Cullens."
Stephine Meyer might not make Midnight Sun.
Its called Zephyr.