When asked about it, he denied the image in and of itself meant anything. He said it was illustrative like a pinup. He said that none of the images used for covers have actually happened in the story. And someone pointed out that the cover of chapter 5 actually happened, to which he did not respond. So, who knows?
Regarding the cover, as usual it's just illustrative, and none of the covers have actually happened within the story; it's like a pinup.
(that was not accurate, how was pointed out but another user).
There won't be a third person or anyone besides Lucas during the relationship.
But reading the Histerycal negative reaction to the possibility of BDSM I think Nandof will discard it, unless any sub pay good money for it.