I was looking at some of the giant salamanders' photos, I think on the Japanese one they have quite smooth slimy skin but on the Chinese one their skins have some kind of knobs and bumps, also slimy.
I'm a lazy person so I took the easy way out which is the smooth skin version. I have kept the body quite straight so I don't have to do too many creases on the body (they do get bunched up quite a bit, the skin is very loose on these animals) . Beside I think people rather seeing the animal that way because it would make it easier to see the length of the animal.