Does age factor into the creepiness factor?
To me a "fresh" skull is creepier than a 100 year old skull.
Would you have a skull in your house? Would you have the skull of someone you knew in your house? Would the skull have to be a certain age? Would it matter if it was the skull of, say, Don Knotts? Would it matter if it Don Knotts' skull and it was wearing a jaunty deputy sheriff hat? John Ritter's skull?
4hour_ramona and beatnikside had some interesting thoughts on the matter. "Any skull older than my dad is old enough."