Hey Mexus! Welcome to Cubebrush. I know you'll continue to grow with your stay on the site.
Now time for some good ol c&c 
For the first image, I recommend making the gun bigger/longer. The gun looks to be on the small side of something that needs 2 hands to carry. Another thing regarding the gun is that it appears flat. There isn't much depth to it. To me the gun looks really skinny. Other than that everything is awesome. Good rendering of the forms and materials. The rim and bounce light work great.
Now as far as the octopus skull demon creature, first it look cools. What I would look at is the contrast of values for the creature. I recommend framing the image. You can do this by darkening the sides of the canvas. There's not much going on in those areas so our focus can be more on the creature. You can brighten up some of the values as well. The range from black to whites aren't very big. The image appears more on the dark side. The red is a dark value even though is looks somewhat bright here. If the face of the creature is where you want viewers eyes to go, Up the contrast in that area. Adding in another light source other than the red in the background will help as well. Maybe something coming from the front so then you'll have a good 3 point light set up. Red back light, Blue bounce light and whatever color you choose to come from the front. Other than that, cool design again for the creature. I like it.
For the final character, its a good start. I like the design and the colors you having going on. Red and gold always look nice. You might need to add a bit more colors to the gold but its fine for now. Guessing your going for a matte like metal?? Try adding a bit more reds the fleshy areas of the skin like the bicep and chest. His belly is a fat belly so the line the middle isn't needed really. But that can be personal preference. Keep up the good work man. You have a lot of cool works here.
