http://dictionary.reference.com/search?q=effigy

And I've already pointed out that the article makes no reference of a disembodied head on a pike a la Vlad the Impaler.

"The drawing that drew the most notice showed a man in what appeared to be Middle Eastern-style clothing, holding a rifle. He was also holding a stick with an oversize head of the president on it."

I'm pretty sure that if the kid drew Bush's head impaled on a pike, the article would have mentioned it.