Feed dialog will not get you this customization you will need to use Open Graph actions.
https://developers.facebook.com/showcase/pinterest/
Also for full width photos from applications, the user must have generated the photo from the app so that you can utilize "User Generated Photos"
For example the following is from the Tumblr application
https://developers.facebook.com/docs/opengraph/howtos/adding-photos-to-stories/