This is the largest image I could find (though I only had a quick look). Obviously it does have the logo and title but they shouldn’t be too difficult to remove 👍
^ Image can be found here - https://romanian-headline.blogspot.com/2021/04/star-wars-new-hope-book-pdf.html
Some of the generic custom cover websites listed up in the An Index & Help Thread for Case Covers, Disc Labels, and Fan Art… thread may also have a decent quality image.
Good luck with it 👍