At present to the best of my knowledge there is no standard for including album art in vorbis comments.

This would be fine, as it generally makes very little sense to store the albumart IN the song file; firstly because it is not metadata for the song (it's metadata for the album the song belongs to), and secondly because this approach stores the albumart once for each song. Instead it makes more sense to store the albumart image, and reference it using the song's tags/vorbis comments.

I don't understand why the media player doesn't support ogg out of the box (particularly given the open nature of the device), but it has certainly caused a raft of problems for the ogg-support package:
- No DISCNUMBER support
- No configurable albumart paths
- No gapless playback (at least I hope this is ogg-specific, as it would be a fairly heinous oversight)