Chouby on ""Translating" untitled posts containing only images with Polylang"

Polylang does not offer this possibility. However, if you have some PHP skills it should be achievable using the functions get_posts to query the posts you want to translate and wp_insert_post to create a new post. Once you have the two posts, you can do something like this:

global $polylang;
$polylang->set_post_language($translated_id, 'fr');
$polylang->save_translations('post', $translated_id, array('en' => $original_id, 'fr' => $translated_id));