Ogg vorbis cover art

How does mp3tag support cover art in vorbis comments? I am still only vaguely familiar with the format but I think it can be done twofold: inside stream and as separate tag field. I ask because for one album my winamp sees the cover art but mp3tag does not.

Later edit: My bad. I just realized winamp reads cover.jpg from folder. Anyway my question still stands.

Even later edit: I've already answered myself. METADATA_BLOCK_PICTURE. Now can anyone be kind enough to recommend a player that actually displays it (windows/linux/android).

Also as a sidequestion is there any way to know what quality (number like e.g. "5" not actual bitrate) a VBR file was encoded?

I'm having trouble with my apps recognising the METADATA_BLOCK_PICTURE artwork tag in my ogg too. Is there any way to convert these to the legacy COVERART tag or maybe an option to do so?