As long as the scarecrow has an entirely flat face I think it’s okay, though some Poskim would be Machmir in that case.
There is an Issur D’Oraisa of Lo Sa’asun Iti, which we assume means (in very un-Maimonidean fashion) that one cannot make a Tzurah of a human face.
(BTW HaLeiVi, if you want proof of Rashi’s corporealism see what he says on Lo Sa’asun Iti, Al Tikri Iti Ela Osi on the Gemara in Avodah Zarah. It doesn’t get much more B’feirush than that.)