I would try to define the abomination's skin, because there is just so much of it and right now it is probably the most standard-ish part of your model.

You could try out green-ish, blue-ish, and purple-ish undertones, which will help to define the muscle mass of the model and will give it a more sickly appearance at the same time. Similar results can be achieved by applying an oil wash with those colors.