Nice work!

I think there's a lot that's good about this piece, yet a lot that can be improved. Here's what I picked up:
- The outlines are what is hurting it the most. Some areas have an outline, some don't, and some have varying shades of outlines. I suggest you just stick to a single pixel-thick outline consistently around the drawing, since it's a bit toony. From there you can try to do selout, but you need to be careful with it so that it doesn't remove the outline, but rather just makes it blend into the color(s) the border is surrounding.
- Quite a few jaggies, and the arms are all inconsistent in how thick they are. The length of them seems about even, though.
- The shading doesn't seem to be clear on the actual tentacles themselves; it makes sense on the head/body, but on the limbs the lighting looks like the source of light is coming from tons of different directions.
I made an edit that took these things I noticed into consideration, and tried fixing as a result:
Original:

Edit:

I then made another small edit on top of that with better AA, selout, and some very simple added detail (just to make the body a bit less bland to look at):
Edit2:

Just my USD0.02 on this piece

again, nice job on it.