This isn't art from the iTunes store. It's old artwork from my files. Why is it changing my artwork at all when I update iTunes match?
MAN! I am in the SAME boat! I had a fix but with the new version of iTunes my fix is bust. Before I did the same as you, disabled iTunes Match did all my artwork changes, enabled iTunes Match and all the artwork stayed hi-res (didn't replicate to iOS devices but that is a known issue.) So after updating to the new iTunes I noticed the majority of my artwork was back to old crappy low-res AND some of my albums I REMOVED artwork (live shows so I just put a picture of the band or something) are all back. So I then disabled iTunes Match again, got my hi-res artwork back (long story short have a doug script that will re-import artwork if the artwork is in the folder with your music. This was a HUGE pain to do but glad I did since my artwork can change all the time.) I then went over to my Air which is just a iCloud for iTunes and went to the albums I didn't want artwork removed those...double checked and made sure they were removed. The SECOND I enabled iTunes Match ALL those that I just removed artwork were back and I was afraid it was going to jack with hi-res scans so I immediately turned it off...and all my hi-res scans are good.
18,596 songs I need to change artwork on I do not want to do this every couple of days...VERY annoying.
If you want I will help you find scripts that will save artwork into folder and then reimport artwork very easily. The reimport artwork can crash so its best to watch it and make sure it finishes or you know where it crashes. I have not found a better alternative.
My next step is to go to ALL my iOS devices and disable iTunes Match...so NOBODY is using it and then go through the steps above and try it again and see if it will keep artwork off and keep good artwork there. SOOO annoying and I feel your pain 1000000%
