I'm assuming you're referring to the use of your paperback cover being used for hardcover. If so, you won't be able to use the same image if you're using a one-piece cover.
http://www.lulu.com/en/help/book_covers_faq#onepiece_dimensions The FAQs here indicate that paperback and both versions of hardcover books use completely different formulas to determine the size of your cover. Because of this, your paperback cover will not work for a hardcover book. This is because not only is the typical front, back, and spine involved, but there's also the "leaflet" that wraps around and into the book (for dust jacket) or the top edge extending inward (for casewrap). You'll need to add extra content to your cover for these areas in order for it to work with hardcover books. The front and back are essentially unchanged, but the spine is slightly different due to the "indentations" adjacent to the sides. I've never used the wizards as I've used the one-piece cover method (for paperback), so I don't know if there's any differences there but I'm expecting that there will be due to the additions to the edges.
