This image, in this measure or proportion, already exists here in TMDb.
But it is not a Poster. It's a Backdrop, a Fanart.
See here:
https://www.themoviedb.org/movie/354912-coco/images/backdrops?image_language=en
https://image.tmdb.org/t/p/original/sKRnZJ9EDH22o4OvJ7erOmQhQy4.jpg

Right, and in order to have these "back drops" be seasonal, you either need to have seasonal back drops or expand the "poster" sizes to allow for seasonal "back drops". This has more to do with apps syncing with the API than it does being allowed to upload an image.

Sorry, English is not my native language.
I believe I am not understanding correctly what the issue is.
Better wait for Travis Bell to answer your question.

Is the ask here by @irkillroy to add backdrop support to TV seasons? The original post seemed only related to movies and we've supported backdrops since day 1 so I’m just looking for clarification.

I read the OP as support for the new TV app formatting of the artwork. It's 16x9 now, but when I'm trying to upload the images for the season, they don't allow that file size. They only allow that size for the back drops for the show itself but not for each season so Apps using the API can't get the different image sizes for the seasonal image... geez that seems repetitive to me.

There are no immediate plans to add support for backdrops to seasons. I've created a new ticket for this here.