Gallery full of album art in Android?

The solution is simple: change all the cover.jpg or album jpg files to albumart.jpg and they won't appear in Android Gallery.
Of course, if you've bought a 32Gb SD card and filled it with hundreds of albums, this is going to be a bit of a chore. (That's not a lead up to a solution, just a bit of British sarcasm.)
While I'm on the subject of album art, if Android music player is showing the wrong thumbnail image for an album, because you have images for the back and inside of the CD in the music folder (and because the music player is not able to recognise that the image file labelled cover or album is the one it should use) delete image in the Android albumthumbs cache as described here.