Currently doesn’t seem to be a way to pull them or change them, I even unmatched and re-matched. I also added the logo as logo.png in the folder next to the poster.png I am using, no dice.
I had a TV show that didn’t have a logo and I added it in TMDB and it still wasn’t showing up. What I did to make it show up was an abbreviated Plex Dance. I moved the show’s directory out of my TV Shows folder in the file system, then emptied the trash for the TV shows library, then moved the show back in the file system.
After doing that the logo updated in the Preview app.