Before you start worrying about background details, I would focus on making the body/eye more interesting like you said. I imagine the subject would have a slippery, rubbery texture but that's not reflected in the lighting. I'd recommend playing around with specular highlights!
Also for the eye, it might help to think of the iris as a concave disc. The iris would receive light on the side opposite of the light source, but the transparent surface of the eyeball would catch the light directly, creating two distinct highlights. Hope that helps!

EDIT: I just noticed you have a highlight along the left side of the body, which is making the squid look flat. Focus on using light to define the subject's volume.
