In the color of the creature, the sepia. :D
AA that thing. The lines are so sharp they cut my stare!
Thanks to Manupix, I now know that is NOT a mouth...
And the third point that's already stated, is something I agree with as well: Put in some more colours. It's grey on the same kind of grey on the same kind of grey. It's rather bland and boring that way.
It doesn't really look like a a cuttlefish, it's not holding its tentacles the way they do, and there's not enough of the rest of it to clarify. The eye can be mistaken for a mouth.
No AA can be a valid option, but before that the issue is the lines: are they as clean and smooth as possible (no!).
There's a pixel by pixel job to be done, checking each step at 200%.
Agree about contrast: the tentacles need more of it; I'd also recommend some hue shifting (even staying within sepia tones, a little more warmth of tones wouldn't hurt).
Damn, Doesn't look too clear then, it's supposed to be this http://www.medicina-integrativa.net/wp-content/uploads/2013/01/common-sepia.jpg
I really wanted to stay away from AA as I wanted it to be really simple, just tentacles and the eye. I'm sure that when you check the picture you'll see mine better.
Could use some AA and some contrast. What is it, exactly?