Show Preview Thumbnail: Whether or not to display media on posts.
Note: For the “Overlay” layout, if this setting is checked then the image from the post will be displayed. If no image is available then the image added by the user is selected. In case the user has not uploaded an image, the default fallback image is used.
If this setting is unchecked then the user uploaded image will be used for all posts. In case the user has not uploaded an image, the default fall back image is used.