We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Book Cover Design - Proceeding ahead prior to finished manuscript
My manuscript is almost complete, but I am waiting on some additional information. Can I proceed ahead to work on a design for my book cover while I am waiting for this other information, and then go back to make changes to my manuscript (book text). I do not want to be locked into what I have written so far. - Brian Hinkley