This gives me ghost of Danny Zuko vibes. I have thought it was a skull, but I also think it kind of looks like a hockey mask, so maybe it's supposed to be Jason Voorhees.  I think that is completely up to you. 
I made this pendant with clay and kind of resin in a mold, then painted it and added it to a metal cameo frame. The pendant is about 2 inches, and the black chain is about 10 inches.