A thing I noticed ( more of a problem in the first picture rather than the second) is that you use a lot of black and white for your shading. Using black for shadows will make things darker, but also more grainy and dull. I would nearly always recommend using colours for shadows. Usually you can use a blue hue for shadows and darker parts, I tend to find it looks a lot more alive and vibrant.
The hair is also pretty bad, I would advice against making it purple but if you desperatly want to keep it the same colour, you should add some bright highlights /shadows at the edges of it to seperate it from the massive block of purple behind it. Anatomy wise I really do like your hands, although the fingers of the right hand seem awfully smaller when compared to the left hand.
The midsection is a bit wierd with how triangular it looks, but that might be just me. You culd do some work on the shins, mainly the back part of them, if you study anatomy you´ll find that they are more curved than the front part.
The toes look a bit wierd, generally they shouldn´t be able to bend that far.
Although I sorta like the tentacles ( especially the ones interacting with his hands) The shading is really jarring. I would advice using a whitish purple instead of straight white. Or atleast make the gradients softer, the rightmost tentacle works a lot better than the bottom ones for example.
The background takes a lot of attention atm, it becomes hard to see both the hair and the tentacles when they are the same colour. You could try lowering the saturation / contrast in the background but I would play around with different colours.
Don´t take this huge wall of text the wrong way, I am just trying to give feedback on what I think could be improved in the first picture you linked. Sorry for rambling
