UPDATE: Hi-res image of box set now available!
According to the press release:
In addition to the stunning wraparound cover illustration, the deluxe edition includes never-before-seen full color frontispiece art on special paper. There is also an "Illustration Showcase" insert that features near scale reproductions of Mary GrandPré's chapter openers. Additionally, the deluxe edition includes an exclusive bonus black-and-white illustration that appears at the end of the "Illustration Showcase". The custom-designed slipcase is foil stamped and contains a full-cloth case book that has been blind-stamped on the front and back cover with foil stamping on the spine. The book includes full-color endpapers featuring jacket art from the trade edition.
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 GrandPré 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 deluxe edition, with work done by Mary GrandPré and available on July 21, will be a total of 816 pages; the suggested retail price is $65.00 (currently $39 on Amazon.com) and the print run will be 100,000 copies.