wow, that's some really nice work!
considering that you want some harsh critiques for your chow i will start here:
overall, i think it has potential, one thing that is missing for my taste is maybe a more characteristic creature? i have no "face" that im connecting with it when i'm not looking at it.
also the green background is a little boring, you could bring in some different hues for example.
the composition is fairly simple, but it is ok i think.
besides that i like the textures very much, also the glowing tentacles.
hope it helps, cheers