Just sharing one way to add facebook and twitter image meta tags dynamically in landing page:
Step 01) Add the code bellow in base.html.twig from theme.
Note: See in the end of article the meta tags for title and description too.
Step 02: Create a folder called "LandingPages" in the Mautic FileManager
Step 03: Add the pictures [facebook] and [twitter] in the folder LandingPages with the follow structure.
Replace the XX for the LandingPage ID according to Mautic.
Additional information: Meta tags for title and description too.