to me, the apple represents forbidden love, or the "forbidden fruit", and the pale arms represent the vampires.
its all about choice. the cover itself is like, you have a "choice" to take the apple, even though its forbidden. the choices bella and eddie both have to make are the same. do they avoid each other for bella's safety? do they become friends? should they stuff it all and become MORE than friends? (heck yeah
the flower is kind of wilted, and that little petal falling from it looks like a tear to me, so i think it represents Bella's broken heart. the flower looks pretty, but you can see that its dying. Also, the red fringes around the edges of the flower, look a little like blood.Eclipse
i think the ribbon represents the sort of love triangle between eddie, bella, and jake. mostly from bella's POV.
the tear in the ribbon, is NEARLY broken, but is still attcached a little, representing her friendship with jake, and how its not completely over, and there is no clean break.Breaking Dawn
i think the chess pieces symbolise the fight between the vampires, and the Volturi, fo Renesmee.
the firght itself reminded me of chess, two different sides. other than that i really have no idea