Try thinking a long the lines of "get the ball rolling", when designing interfaces where some regions must start from a blank slate, e.g. use placeholders, prompts, etc.
In my experience even seasoned designers do a poor job of this. They show you comps of with the perfect set up -- everything populated, beautiful photos uploaded by the user that are perfectly square, 100 comments on very post (or whatever the analog is for your app).
I've gotten a lot more insistent that designers show me "empty" designs where the user has just signed up and various corner cases like a photo that is really tall.
I've gotten a lot more insistent that designers show me "empty" designs where the user has just signed up and various corner cases like a photo that is really tall.