Is there a way to add additional marketing images as to provide more of a preview?
No, because it's also the 'Book Cover'. It will eventually be added as the first 'page' of your ePub and will also be used as the display icon.
As per >> http://www.lulu.com/shop/kevin-lomas/keep-that-noise-down/ebook/product-22304800.html
No, but you can add as much of a preview as you like at lulu. Retailers also provide a preview of the book. Usually 20%.