There's no doubt that people are attracted to facial expressions. Silhouettes prevent us from seeing those cues we often seek to imagine how someone may be feeling. That's OK though. Silhouettes can have a bunch of emotions drawn from a viewer with the right photograph. All the elements in the scene from lights. color, structure can add to the silhouette of a person, to create feelings.
A great silhouette can capture joy, pain, fear, love, loss and more. One exercise to try is to create a fictional character that you will take a silhouette photo. Find your scene and if you want add costumes. Decide what backgrounds you like and if you want to add another person for more drama. What you add to the photo adds to the effect of drawing emotions from your viewers. Challenge yourself with various scenes and characters.