There are many options when you create your cover. You can choose to have a photo that wraps from the front of your cover over the spine and onto the back of your book or you can choose different layouts for the front and back of your book with different images, text, and backgrounds. (Note the red arrows which indicate different parts of your cover.)
To change the layout, you can simply choose whichever photos you want, drag them up to the page and place them as desired.
There are dashed lines that indicate approximately where your spine will be. Please note that the spine in the editor does not adjust depending on how many pages are in the book, so these lines are only approximate. You can see more about our custom covers and spine text here.