the album art is embedded with the files. those are all downloaded MP3s via some third-party app, some show album art out of the box, others blank. iTunes is just pulling up the album art as Android would, except that in the first pic above, those songs are not MP3s and are stored online via Play's unlimited access, so the album art comes from their end.
often times with downloaded music, the album art is not accurate. i got one song (C.W. McCall's Convoy) that has album art of a chimp sticking his fingers in his ears. other songs have used the album art not fitting for their artist. a few dozen i'm working on deleting and replacing have the same Midnight Oil cover art despite not being a Midnight Oil song.