It's stuff like this that makes you see just how evil Black Shadow and Blood Falcon really are. In the games and in the anime, Black Shadow and Blood Falcon are evil, but in a cool way.
But in this continuity they are just sick and cruel. I seem to recall Blood Falcon asking if they should "practice" on Rose.
The silhouettes do an excellent job of highlighting not just their blacken souls but really ups the intimidation factor as well.
They help convey the image of an abused child locked in a closet without light for hours, only to dread the light that comes with the open door because they know this light does not bring salvation, but the news that their abuser has returned ready to go another round.