We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Changing the cover of an e-book that has already been published on the Lulu site
I published my e-book a few months ago and used the default cover image (plain black background). If I want to change the cover, customising it using a new image, what do I need to do? Do I need to use Photoshop on the image to resize it and add the title etc before uploading? Any advice on successfully customising the cover art for an e-book on Lulu would be much appreciated. Thanks. Brian