Hi,
I originally had a book cover feature but removed it because the people who were going to be using it at first, didn't want it.Ê If you have all of the book covers in an easy form as you say, then it wouldn't be too hard to re-add this.Ê The easiest way is to probably add a column to the books table for the cover art.Ê Then implement an htmlValue method in books delegate class (tables/books/books.php) for the column to make sure that it is displayed as an image.
You'll notice remnants of the old columns named cover_art_url_large, cover_art_url_medium, and cover_art_url_small that are already in the fields.ini file and the books.php file.
To make life easier, you may want to just name your field cover_art_url_large so that it will pick up the existing settings.Ê Then you should be able to do one big SQL query on the database to populate that field with the correct cover art url values.
You can alter the cover_art_url_large__htmlValue() method as required to make the output how you like.
-Steve