I have been reading some wonderfully creative theories! My own contribution to the nuttiness is in the comments.
From the Scholastic Press Release: David Saylor, Vice President, Creative Director, Scholastic described the art as:
Set during a highly dramatic sunset, Harry, Hermione, and Ron–clothes in tatters–cling atop a flying dragon in this astonishing artwork created by Mary GrandPre for the deluxe edition. As mist creeps down towering hillsides to a village below, questions arise about where the trio is headed and what has led them to this spellbinding moment.
The covers were revealed this morning by Arthur A. Levine on the Today Show (NBC). According to their webpage, "Arthur said the image on the cover is one of his favorite scenes in the book and he specifically asked that it be the image of the deluxe cover."
Usually there is also bonus art inside the deluxe edition. According to the press release, Here’s what we still haven’t seen yet:
* never-before-seen full color frontispiece art on special paper.
* "Illustration Showcase" insert that features near scale reproductions of Mary GrandPre's chapter openers
* bonus black-and-white illustration that appears at the end of the "Illustration Showcase"
The deluxe edition will be a total of 816 pages; the suggested retail price is $65.00 and the print run will be 100,000 copies.