Media may be attached and retrieved for Direct Messages through authenticated calls with app-user authorization.
Direct Messages with an image will contain a media object with relevant details, check our Twitter data objects dictionary for more details here.
Uploading and attaching media (images, GIFs, video) to a Direct Message.
Retrieving Direct Message media
For media in Direct Messages
media_url is the same https URL as
media_url_https and must be accessed by signing a request with the user’s access token using OAuth 1.0A.
It is not possible to directly embed these images in a web page.