These can be changed relatively easily. Whatever images are used are stretched to cover the whole pages.
If we were to actually print this then the front and back covers would be somewhat larger than the pages. I haven't bothered with such details here. Plus we'd need a spine.
You found Waldo! % we need some kind of text for this page to actually be a page. a ~ would be enough but this is more fun and is covered up by the actual cover image
\newpage
This is the inside of the cover. We could put stuff here.