I've done a bit more testing and research and it seems you cannot prevent vlc from downloading external album art (except by switching your router / modem off). This is probably by design because it seems from amazon.com there are royalties involved. I have also experienced the wrong cover art being downloaded (apart from the weird experience with remote tagging I described earlier). But it seems this is because there is not enough information in the other tag fields to uniquely identify the required cover art. For example, if you use mp3tag -
www.mp3tag.de/en/download.html -an excellent utility - specifically the options to download cover art or tags - you will get a number of options depending on how many other tags you have specified. Hope this helps a bit...