Since a cover gallery or thumbnail view does not seem likely to ever be developed, how about adding the UPC codes to the scrollable list of data to help in locating an issue. It would give the servers a break, because we wouldn't have to click on every single issue and load the cover to find what we are looking for.
Click on the little blue image on the left of the issue number. You can then scroll through ALL images using the prev/next links. When you find the one you want make note of the Issue # with it, then you can click on the Issue # if needed.
There is no room to add the UPC to that list. Also not all books have a UPC as well as several publishers use the same UPC for multiple books.