I don't have a better place to leave this.
If you are using iTunes for Windows and have imported music into your library through various routes, you might have a problem with missing or incorrect album art. This is especially a problem with Classical music. Apple will look up the cover art if you right click the album and select "Get Album Artwork" and wait a moment or two. It works well for popular music but can't find anything for less popular works. Often, ripping a relatively new Classical CD will yield no cover artwork when the songs import into your library.
The newer versions if iTunes have a slick way to update the cover art. Just select all the songs in the album, right-click and pick Get Info and an edit box will pop up. Click the Artwork tab near the top center of the screen, and copy the artwork to the white area. But where do we get the artwork?
Now, the magic. This requires you use the Chrome browser, non-maximized, so you can see at least a bit of your desktop on the bottom corner of your screen.
Type the artist name and the album name in the address bar. It's important that this get to Google as a search. If you've configured your browser to work differently, just go to google.com and type artist name album name into the search box.
One way or another, the search will come back, and the Google results page will have a link to Images. Click that. There's your album cover! Now, hover over the images to find one that's around 300x300 pixels in size. 500x500 isn't too big, and 200x200 isn't too small. iTunes can handle it. Drag the image from the Google results page down to the visible part of your desktop and drop it. There will be a small image file on your desktop, named imgres.jpg. If you've done this before, there's another one there already, and a confirmation box will pop up. Click "Replace existing" and it will automatically overwrite the last one with the current one.
Now, select all the songs on the album in iTunes, Ctrl-I (or right-click, Get Info), click Artwork tab, and drag the artwork off your desktop onto the white paste area, and click OK. Presto. Go find the next missing album cover. Rinse and repeat. I love how this works so seamlessly, with an absolute minimum of interaction with the OS, and no messy files to keep track of or clean up.
This works in iTunes running on versions Windows 7 through Windows 10. This method doesn't really require the Chrome browser, but it takes advantage of the nice Chrome feature integration with Google image search and how images found can be just dragged and dropped onto the desktop. I've used this method to fix covers on literally hundreds of albums in my iTunes library.