Add cover art that iTunes downloaded so it's embedded into the track directly.

Add-DownloadedCoverArtToFile.js

// Add-DownloadedCoverArtToFile.js
// By Travis Illig - http://www.paraesthesia.com
// THIS SCRIPT MODIFIES YOUR ITUNES TRACKS TO EMBED DOWNLOADED
// ARTWORK INTO TRACKS. USE AT YOUR OWN RISK. BACK UP YOUR FILES
// BEFORE RUNNING.
//
// Open iTunes, then run using cscript:
// cscript Add-DownloadedCoverArtToFile.js

// Set MAX_TRACKS_TO_PROCESS to the max number of tracks to process
// in a single script run. Since artwork processing can take a long
// time, if you have a large library you may not want the script running
// for hours to do the whole library at once.
var MAX_TRACKS_TO_PROCESS = 250;


// DON'T MODIFY BELOW THIS LINE
// unless you know what you're doing. :)

// Get the set of all tracks from the library.
var iTunesApp = WScript.CreateObject("iTunes.Application");
var allTracks = iTunesApp.LibraryPlaylist.Tracks;
if(allTracks == null)
{
	WScript.Echo("Unable to get list of library tracks!");
	WScript.Quit();
}

// Initialize some global values we'll use later.
var scriptWorkingDirectory = WScript.ScriptFullName.substr(0, WScript.ScriptFullName.length - WScript.ScriptName.length);
var fso = WScript.CreateObject("Scripting.FileSystemObject")
var numTracks = allTracks.Count;
var completePercent = 0;
var numProcessed = 0;

// Process the tracks.
for (var i = 1; i <= numTracks; i++) 
{
	var currentTrack = allTracks.Item(i);
	
	// Only handle local tracks that aren't podcasts and that have downloaded art.
	if(
		currentTrack.URL != null ||
		currentTrack.Podcast ||
		currentTrack.Location == null ||
		!HasDownloadedArtwork(currentTrack))
	{
		continue;
	}
	
	// Only handle tracks with ONE piece of artwork. If a track has multiple pieces
	// of art, the order can be important and that's not something we want to deal with.
	if(currentTrack.Artwork.Count > 1)
	{
		WScript.Echo("WARNING: '" + currentTrack.Name + "' has " + currentTrack.Artwork.Count + " pieces of art, one of which is downloaded. Process manually.");
		continue;
	}

	try
	{
		WScript.Echo("   * " + currentTrack.Artist + " - " + currentTrack.Album + " - " + currentTrack.Name);

		// Extract the art to a temp file, embed it in the track, and delete the temp file.
		var tempFileName = scriptWorkingDirectory + CreateGuid() + ".bmp";
		var artToSave = currentTrack.Artwork.Item(1);
		artToSave.SaveArtworkToFile(tempFileName);
		artToSave.Delete();
		currentTrack.AddArtworkFromFile(tempFileName);
		fso.DeleteFile(tempFileName);
	}
	catch(ex)
	{
		WScript.Echo("Error processing " + currentTrack.Artist + " - " + currentTrack.Name + ": " + ex);
	}
	  

	// Provide a percent complete status message.
	var currentComplete = Math.floor((i / numTracks) * 100);
	if(currentComplete - completePercent >= 5)
	{
		completePercent = currentComplete;
		WScript.Echo("Processed: " + completePercent + "% of library.");
	}
	
	// Bail early if we hit the max tracks to process.
	numProcessed++;
	if(numProcessed >= MAX_TRACKS_TO_PROCESS)
	{
		WScript.Echo("Ending processing early - reached max tracks to process (" + MAX_TRACKS_TO_PROCESS + ")");
		break;
	}
}
WScript.Echo("Done.");

// Checks a track to see if any piece of artwork associated
// is a downloaded art item.
function HasDownloadedArtwork(artTrack)
{
	if(artTrack == null || artTrack.Artwork == null || artTrack.Artwork.Count == 0)
	{
		return false;
	}
	var artwork = artTrack.Artwork;
	var numArtwork = artwork.Count;
	for (var artCounter = 1; artCounter <= numArtwork; artCounter++)
	{
		var currentArtwork = artwork.Item(artCounter);
		if(currentArtwork.IsDownloadedArtwork)
		{
			return true;
		}
	}
	return false;
}

// Creates a new GUID that we can use as a temporary filename.
function CreateGuid()
{
	var scriptTypeLib = new ActiveXObject("Scriptlet.TypeLib");
	return scriptTypeLib.GUID.substr(1, 36);
}