Thank you very much for the replies. Unfortunately I was pretty bad with time management on this model and didn't have enough time to make proper retopo and texture. But I will do it later, after the end of the contest.
Here are the final sculpt and the weapon for this demon. I hope you enjoyed watching my process, because I really enjoyed making this model and definetely learned a lot.
And, since this is the last day I could work on the model, I tried to render it in marmoset for the final image using just vertex color. I wish I had more time to make it right, but for now - this is all I could do whithin given time. I will do a proper lowpoly and texture later and share it on my artstation page.