To make it more gross, the first thing I thought was to add slime--preferably green

...but I guess any color--from the tentacles all over the handles of the gun, and dripping to the floor and stuff.
And while you're at the gun...I don't want to complain, but its a very plain gun. Yes, it is true that you can go overboard...but it really feels like it is lacking....I'd say at the very least, add in the hand grip under the barrel for his right hand....tentacle. (see
this if you need.

)
The other thing I wanted to point out, is when he looks to his right, and his body goes down...its like the top-half of his body cuts into his chest--I think what would actually happen is that guts/cable (what ever it it, lol) would push the other stuff aside, not just make it disappear.
And I guess the only other minor thing I have to say, is that when the air pumps into the mask, the bulge the mask makes is barely visible--I didn't see it until I zoomed way in.
But other than that stuff, this looks bad-ass

...I can't wait to see this when it's all done and grossed-ified to the max.
EDIT:
I just saw that the gun looks like it's bent when it's facing down...the angle of the front part of the gun doesn't match the angle of the back part---might want to keep that in mind...