Christmas copyright / consent

Hi All, our charity is planning to run some festive posts in the lead up to Christmas which highlight how some of the key messages from our work are touched upon in popular Christmas films. Can anyone please advise if it would be ok to use a still image from the film in social media assets, or if we could find ourselves in breach of copyright? I don't think the posts would work as well without a recognisable image from each film, but obviously don't want to do anything that could land us in trouble! If we'd need consent, does anyone know who we would go about asking for that? Thank you!🎄😊