Take your time
I think that the image lacks in the detail when it comes down to the finished product. You've got a decent enough concept, but the real value would be shown by taking your time in sketching, then spending a little more time in getting the details right.
For example, the tentacles should be slightly more uniform, with tapered finishes from the body down to the tips. Spending time getting this right is very worthwhile and will give you a much better looking image, to compliment the background. Perhaps consider this taper effect on the neck, so that the head looks better supported.
Finally, with the background, I would suggest that you work more on the rift that appears to be where this alien being has been manifested from.
[Review Request Club]