How to change vertical thumbnails back to horizontal in iMac's Apple TV app?

I have a large collection of movies and TV Shows that I have downloaded from a variety of sources over the years. After the last few Mac OS updates started displaying all titles in the TV app as horizontal thumbnails, I spent a great deal of time downloading/creating horizontal Artwork for all 3000+ movies. I updated to Tahoe this week, and am dismayed to see that it now is displaying/expecting vertical artwork. Is there a way to change it back to horizontal thumbnails that I'm not seeing? It would be nice to have the option to configure what my desired grid display is.

[Re-Titled by Moderator]

Original Title: Thumbnails in TV app changed to vertical after I spent HOURS creating horizontal artwork for most of my movies