just a suggestion , you could partner with some fan fiction author there are some very good out there even better that the original book sometimes .
It makes the fan fiction's author a book cover and can display along with his story , creditting the artist ( it makes a bit of promotion to the artist also )
i know one author for exemple who made a very nice story in Harry Potter world , it's an original character evolving on a US wizard school , the story is original , creative and very well written ( personnally i think it is as good a Rowley herself .)
And there are tons of good author right there with no cover art , and as the will never be published ( franchise right etc..) there is no money involved , they are also passionate people , and who knows, it can make some good contacts also for futur partneship if they ever been published .
just a suggestion
cheers