I'm having issues when a user tries to share the URL to a Facebook tab app that I have setup.
When they paste the URL to the tab in their share window and then post their status update, the tab image is shown when viewed on their profile, however there is no image shown on the newsfeed version of the same post.
I've tried adding open graph meta tags to the app, but I believe that it is being ignored since it is located inside of the iframe, and the facebook open graph meta overrides it.
Does anyone know how to ensure an image is maintained when the tab URL is shared directly?
I've burnt a lot of time trying to solve this issue as well. The best I've come up with is that Facebook is going to chose to display the 111x74 app icon. Sharing this on a page's news feed makes it very pixelated and oddly offset, as it should be using a 1200x630 minimum image size, as dictated by the OG tag best practices, but Facebook has not allowed us to have that option in the app configs. It may be that your app icon is being offset enough to not appear like it's visible in the news feed.
So, from my research, we're out of luck until Facebook decides to fix this issue. Until that time, I don't think it's even worth trying to get the any image to work.
Someone feel free to prove me wrong.