I think the success of a scarecrow depends on the positioning of the head. I always aim to make the head below or equal to the shoulder height. That gives a sad and lonely and tormented feeling to the scarecrow. Tilt the head slightly and you have yourself a vile prop.
Pumpkinrot's head was fun because it gave the impression that he was looking down at the people passing by.
Johnny Appleseed backfired on me a little bit since the post was placed further back than I had anticipated, and behind a small wooden fence. For the most part, his face was obscured by the rim of his hat and I think a lot of people didn't realize what was under there. That fit somewhat with my original design, since I imagined people seeing his skeletal teeth and leaning in for a closer look only to see his horrible face. But the distance of the post made that difficult so people didn't even bother to peek - which, in a weird way, suited me just fine. Like it was my creepy secret (not good for votes, by the way).
Bog Man is my personal favorite and his success (as a prop) has everything to do with the positioning of his head. Like he doesn't want to be there. Like he's tired of the torment (probably not good for votes either).