Yesterday I upgraded Ubuntu OS from 20.04 to 21.04. After installation, I found an issue with embedded icons in wallpaper that seems part of the image without any use. If I change the wallpaper those embedded icons are still there.
Welcome aboard.
Given what you’ve described so far I’m thinking screen burn. I had the same issue with my cell phone just recently.
Are they still there if you open a document?
Are they faint or prominent?
Can you delete any of them?