Secondly, if you want to have antonyms of posture, you must connect an auxiliary adjective, so that you can have antonyms. This word is not an adjective, so there is only a synonym: body type.
If there are auxiliary adjectives, such as
Obesity posture
, the antonym is
Thin posture
It can be concluded that this word has no antonym.
If you really want to have it, then you can only use antonyms, as well as faces and portraits.