When your out there headbanging on stage, You shouldnt give a shit AT ALL what you look like. Their faces turn upside down because they feel the music, When your really into the music you cant control wut the hell your face does. Look at Randy Rhoades, He is the worlds worst face contorter, and probobly up there on one of the best guitarists ever! I havent seen many pictures of Randy Rhoads were he doesnt look constipated. Face contorting is completly normal and probobly a good thing........gets them face muscles workin......