I have an advanced pass that records all episodes of KTLA news. I've long been annoyed that all of the newscasts have the same artwork, so I can't really tell them apart in Up Next.
I bit the bullet and made images for each newscast. I went to the show page for each hour's newscast and set the art to the appropriate image. I did check the "Apply art to all recordings..." checkbox. This updated the art for the existing recordings, but as new newscasts were recorded, they went back to the default artwork.
In this post Maddox indicates that it should work as I hoped and expected. But I'm unsure if he said what he meant to say or left out the word "not". There is at least one other thread that seems to indicate it is supposed to work as I had expected.