Simplify the whole thing by using taglist types and not bothering with the

config option or command to switch it on

mopidy/mpd/protocol/tagtype_list.py

@@ -19,4 +19,6 @@ TAGTYPE_LIST = [
     'MUSICBRAINZ_ALBUMID',
     'MUSICBRAINZ_ALBUMARTISTID',
     'MUSICBRAINZ_TRACKID',
+    'X-AlbumUri',
+    'X-AlbumImage',
 ]

mopidy/mpd/translator.py

@@ -97,6 +97,12 @@ def track_to_mpd_format(track, position=None, stream_title=None):
     if track.musicbrainz_id is not None:
         result.append(('MUSICBRAINZ_TRACKID', track.musicbrainz_id))
 
+    if track.album and track.album.uri:
+        result.append(('X-AlbumUri', track.album.uri))
+    if track.album and track.album.images:
+        images = ';'.join(i for i in track.album.images if i is not '')
+        result.append(('X-AlbumImage', images))
+
     result = [element for element in result if _has_value(*element)]
 
     return result

tests/mpd/test_translator.py

@@ -14,7 +14,8 @@ class TrackMpdFormatTest(unittest.TestCase):
         name='a name',
         album=Album(
             name='an album', num_tracks=13,
-            artists=[Artist(name='an other artist')]),
+            artists=[Artist(name='an other artist')],
+            uri='urischeme:album:12345', images=['image1', 'image2']),
         track_no=7,
         composers=[Artist(name='a composer')],
         performers=[Artist(name='a performer')],
@@ -76,8 +77,10 @@ class TrackMpdFormatTest(unittest.TestCase):
         self.assertIn(('Disc', 1), result)
         self.assertIn(('Pos', 9), result)
         self.assertIn(('Id', 122), result)
+        self.assertIn(('X-AlbumUri', 'urischeme:album:12345'), result)
+        self.assertIn(('X-AlbumImage', 'image2;image1'), result)
         self.assertNotIn(('Comment', 'a comment'), result)
-        self.assertEqual(len(result), 14)
+        self.assertEqual(len(result), 16)
 
     def test_track_to_mpd_format_with_last_modified(self):
         track = self.track.replace(last_modified=995303899000)