Both the object and the shadow has to have a connection though, a related theme, to both set an atmosphere.
Idea # 2
This image uses the shadows to portray a powerful feeling of emotion and fear.
The picture is taken in an angle to show the girl is not holding a balloon. However, the shadow shows that she is. It looks like she is looking at her own shadow wondering why she is holding a balloon in her hands.
This image has the objects which are parts of a clock and throws a shadow of a clock on the wall.
This picture is interesting because it shows a shadow of a girl in the wall. Also, it shows some birds on the wall or, floor as it seems in a different rotation. It has created a new feel and makes your head turn, literally.