I agree, I think a Predator style shoulder mounted gun would be cool, the tail should just be a tail - maybe with some pincers to grab onto stuff like a big earwig.
I think you could add in some detail on the head - like the pipes going in at the back, a little bulge around the meeting point to make it look like the pipe go into the flesh. Some scarring, and some sort of way that the mask is attached to the face as Ortu suggests.
It's a really nicely made model already though, will be interesting to see how the baked, low poly version looks next to it.
I am the one who knocks...
