During the prologue when Peter Van Garrett is travelling his carriage, he looks out the left-hand window and sees a scarecrow passing by. However, the carriage is moving right-to-left - the perspective is wrong.
You might also notice that Van Garrett passes the scarecrow and some time goes by before the horseman beheads the driver. Yet when Van Garrett runs into the field, it doesn't take long before he reaches the scarecrow again (where his blood splatters on the pumpkin head..a nice creepy effect :) ) Also, pumpkins rot, so the scarecrow's head would have to be replaced a lot.
He couldn't have had his back to the horses because when the driver is be- headed, he leans out and sees the headless driver, his back is not facing the horses, and we never see him turn around. Therefore, the scarecrow was moving in the wrong direction.