Overview
I have seen many projects that put shadowy figures in windows by cutting them out of black paper
and taping them to windows (with a little back-lighting).
You can even get transparent window clings with figures pre-printed on them.
I suggest putting the figures on poster-board,
hung from the ceiling with string at the upper two corners.
Now, if the board moves, the figure seen in the window moves around.
Take an oscillating fan and set it to blow on the board,
so there is always some kind of movement.