Apple has been granted a patent (number 9,135,725) by the U.S. Patent & Trademark Office for "generic media covers." It involves those, well, generic items you see on Apple's online stores, such as iTunes and iBookstore, for digital media items that publishers have submitted without a personalized cover.
According to the patent, a generic media cover can be generated for a media item by "hashing" a unique identifier of the media item that remains consistent throughout the life cycle of the media item. Music producers and publishers frequently add new digital media items for sale on the online store.
However, newly added digital media items can sometimes be received without a media cover. This can happen because the artist/author didn't provide or didn't wish to provide a media cover. In these scenarios, the online store presents the digital media item to customers without a media cover.
However, as Apple notes in the patent, a media item without a media cover is "visually unappealing." This is particularly true when an entire page of digital media items are presented without media covers, which makes it difficult to tell apart one digital media item from another. Apple says this is why there's a need for generic media covers.
Here's Apple's summary of the invention: "Bytes of the hashed value can be translated into graphic parameters which are used to generate the generic graphic. The graphic parameters can be attached to the generic graphic, thus allowing a user to regenerate the generic graphic at a desired resolution at a later point in time. Also disclosed are techniques for ensuring that generic media covers for a bundle of media items appear substantially similar."