The word 'sits for' can mean to pose for a photograph or portrait. Some antonyms for this phrase could be stand up, move, walk around, or fidget. Other antonyms could be more abstract, such as neglecting, avoiding, or ignoring. These words would all imply a lack of interest in posing or being photographed. Alternatively, words such as run, rush, or hustle could be antonyms for 'sits for' in the sense of taking action or being active. It all depends on the context and how the phrase is being used.