Unseeing Eyes!

I have been looking through some images - actually, a lot of images - for suitable posts on my other blog, The Graveyard Detective. I have started noticing some of the heads displayed around the doors to chapels and churches and got to wondering who or what they are meant to represent? Some are striking, others eerie and disturbing. Perhaps one of you, oh sharp-minded followers, knows the answer? Here is one example. I am not enamoured with its unseeing eyes! I'll post a further selection later.