Some people like to add album art as it looks pretty on there colour ipods and things, and some people add totally irellevant album art to everything as they think it is rather clever
In mac album art (if affixed, and it is not usually in my experience) s a part of the id3 tag and can be removed using an id3 editor, such as the one in iTunes. You can delete all your album art in one go usuing iTunes. I think it is a little different in Windows but any id3 editor should be able to remove it. I have a notion that deleting id in the LW library does not work always/ever???
Also another id3 editor is mp3 Rage (now called Media Rage which has better support for other formats such as ogg & m4a) and you can find Media rage via Google.
I hope this helps and have a Happy new year Mike.