I think maybe it's that you've put so much detail into the dimensions of the face and neck area that it might feel like you've underdone the clothes and tentacles a bit. For example there might be a little lacking shading etc etc. That's just my guess.
the color? Though that's obvious. Try blackening the tendrils and suit and adding some sort of velvet visible texture to the suit whilst adding some visible texture to the tendrils amounting to bristles. Might work then.
you know, its finny that you mention that because some of the elements of this picture came from the worst nightmare i had when i was younger! and that's a good idea! I'll play around with that concept a little and see how it turns out