In 10.9, NSUserNotification supports a new property "contentImage", which allows the use of a graphic within the notification itself. I was really hoping that there might be a way to usurp the notification screen ala iTunes' notifications, so it would appear as if the sender/bundle app icon is customized.
But it appears that the property only allows for a subset of what I'm looking for, and the contentImage property only handles images thusly:
Any ideas on a workaround?