Is it possible to delete images from the wallpaper folder on android?

I downloaded a photo from facebook, and set it as the wallpaper on my phone, then decided I wanted to remove it again. The problem is, I have not yet been able to find a way to delete photos from the wallpaper and lock screen selection. I can understand that they might not want me deleting the stock ones, but it seems there is also no way to delete the ones I loaded. I am on the Oneplus 3T, if that makes any difference. Also, I deleted the photo from the downloads folder, but it still remains there as an option for a wallpaper or lock screen.