Music covers aren't shown correctly
iTunes and Windows Media Player encode album art into the song file's metadata.  Googly Play Music uses an 'old hat' method for adding album art.  Linux or WinAmp users know about this.

In your Album directory drop the image of the album in the directory and rename as "AlbumArt.png" or "AlbumArt.jpg".  (Note the capitalization).

Google Play Music should pick it up, if not the artwork may not have fully synced.  Try resetting your droid and it should re-sync. :)