Have you looked at the TFA Art book or the special features on the Deluxe Edition blu-ray? That gash isn't even the half of it. His body is all ****ed up.
Something cool: Snoke's top K9 teeth are shaped...like a vampire's fangs. Obviously Snoke isn't a vampire, but the design team mentioned that the Hammer Horror films were an inspiration for the design of Snoke. So it's neat that they gave him teeth that we associate with vampires. He also has pointed black claws.
Oh and the purple gums could either be something unique to his species...or it could be due to a lack of oxygen because he doesn't breathe...because he is dead and being animated by a dark side spirit or some other mystical dark side mechanism. Seriously, look at him and tell me he doesn't look like a corpse. Just something to think about.