The iOS 8 Music app on the iPhone heavily emphasizes album art, displaying the cover artwork for each song as it plays and showing a layout of all your albums when you tilt the phone on its side. If you're missing artwork, however, this stylish design turns into a sea of gray squares. To obtain the covers, use iTunes on your computer to find all the albums with missing art, and then either download the art from Apple or import it from an image file. After adding the art in iTunes, sync your phone to send the pictures to your device.
Identify Missing Covers
Apple removed the cover flow for iTunes 11, but the default view in iTunes 12 displays a grid of album covers. Any covers that display a musical note on a gray background are missing art. If you prefer the traditional list view, pick "Songs" from the View drop-down menu, and then check "Show Artwork" and "Always Show" to display cover art. Scroll through the list to find which albums need work.
Download Art in ITunes
If the iTunes Store sells the album with missing artwork, you're in luck -- even if you didn't buy your music through Apple's store, iTunes can download art for any disc it offers. Right-click a song or album that's missing its art and choose "Get Album Artwork." Check "Do not ask me again" to speed further art requests and press "Get Album Artwork" to send the song's info to Apple. To check several songs or albums at once, select them simultaneously by holding "Ctrl" and clicking each, or by holding "Shift" and clicking the final item to select. If no art appears on an album, the iTunes Store does not offer the album you chose.
Add Art From a File
To fill in the gaps that iTunes can't download, you'll need to find and save the artwork from elsewhere. If you have a physical copy of the album and a scanner, scan its cover for a high-quality image. Otherwise, search for the album by name on an image search engine or a Web store that sells CDs. Right-click a picture of the artwork and save it to your computer. Try to find a picture at least 500-by-500 pixels large to avoid a grainy image on your iPhone. Select the album in iTunes, press "Ctrl-I" to open the Info page and switch to the "Artwork" tab. Click "Add Artwork" and pick the file you saved. After adding the art in iTunes, you can safely delete the file you downloaded. As a shortcut, right-click an image on the Web, copy it, select the missing album cover on the info page and press "Ctrl-V" to paste.
Fix Broken Art
On occasion, iTunes 12 stops displaying art for albums that already have art downloaded. If you open the Info page for a song and see the cover displayed at the top of the page, click "OK" and the art should work correctly. To fix many albums at once, delete the iTunes art cache. Quit the program, press "Windows-R" and run "%userprofile%\Music\iTunes\Album Artwork" to open the art directory. Delete the Cache folder and reopen iTunes to regenerate the cache. If that doesn't work, run "%appdata%\Apple Computer" and delete the iTunes folder. This method resets a few settings in the program, but you won't lose anything from your library.