Controlling the 'favorites' icon
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When users install an app on Facebook, as we all know, they can make the app a favorite on their timelines.  However, we're seeing that the icon itself isn't what we expected it to be.  I had assumed it would be the banner image that we upload when creating the Facebook app.

In actual use, the app icon image changes, and contains images that a user has included in our app (we post real estate listings to Facebook.)

My question is, is there a way that we, the developers, can control what app icon is displayed on a user's timeline?