What is this called?

Are you talking about the name of the flowers or the item itself?

I would say canvas or curtains.

I'd probably search for a mix between Jasmine and Tammy's suggestions and call it a screen backdrop.

What a beautiful piece of décor!! 🤩

It's definitely a ceremony backdrop, and looks like a silkscreen printed fabric / canvas stretched tight in the backdrop frame - with floral accents added on top!! 🌺

I'd take this picture as your inspiration to a florist or wedding decorator to see what they can do! Or if you're trying to DIY, it might be easier to search for "ceremony backdrop frames" and "printed backdrops" separately!!

Backdrop, privacy screen, printed canvas screen. It could be any of those, or none of them. But that's where I would start my search.