Retrieving the Cover Downloads option
When importing a CD or adding new song files to iTunes, album artwork may be missing and iTunes may not automatically download and add it.
Check if iTunes has been configured to use this feature. You can enable this feature in iTunes Preferences:
iTunes will only download album artwork for songs it can find in the iTunes Store. iTunes will search for each song in your iTunes library and try to associate it with a song from the iTunes Store.
If the data matches, iTunes will download the album artwork from the iTunes Store and add it to the song in your iTunes library. If iTunes can’t find artwork for a particular song in the iTunes Store, you won’t see an alert message. iTunes just won’t download the artwork for that song.
You must have an iTunes Store account and be signed in to the account on the device you’re using.