I love Apple products for their attention to detail.
The Computers app in tvOS 13 lacks that attention when displaying artwork.
Artwork on macOS 10.15 Catalina is now horizontal.
Computers displays movie artwork vertically and TV programs as a square.
Movie playlists display a square, forming a black box around existing artwork if necessary.
When viewing Unwatched movies and TV programs, the bottom of any artwork is cut off. This is especially noticeable with movies.
TV program episodes are displayed horizontally, forming a black box around the square artwork.
In short, even if I were to adjust the library artwork in Catalina's TV app, it would end up looking disjointed somewhere in the Computers app.