Imagine she was the mother of your infant daughter or son. Would a snake coming out of a skull's eye be an ideal image for your newborn to see each time momma reached into the crib?
Watch out, we have an expert here!Part nature, part nurture. Fear is part of human DNA as a basic survival mechanism. Instinctive fear of things that are a threat (snakes, for obvious reasons, and things associated with death and decay, for less obvious reasons) are innate in humans. Cemented further by social constructs that drive infant learning. Nothing of what an infant sees or hears is going to reinforce skeletons or snakes as good companions. Seeing that image on its mother will, at best, be confusing, and at worst, damage the infant psyche in unpredictable ways.
By the way, I have not one, but two skulls on my body. Neither of my two boys were afraid of them as infants. I can confirm they have not developed any problems or have a damaged psyche as a result of my evil skull tattoos.