I just found that you can rearrange the sequence of multiple album art. Click on a song, then get info. Click the Artwork tab. Click on an image to highlight it, then click and drag it to where you want it to appear in the sequence. Click Okay and go back to the library. You won't notice any difference until you click elsewhere, then click the song again (a bug, I presume).
I noticed this when v.4 first came out, but completely forgot about the feature!