Not bad overall. Composition-wise, the picture does well. The perspective is also done well. You did a good job shading the monster. For all the other parts of the picture, I wish there was more shading - unless it's part of your style, of course.
I have to say I really enjoy this. It's really creative and fun, but also constructed thoughtfully so it isn't a big mess, which isn't easy to avoid when doing wacky sci-fi looking creatures. Your light source is also fantastic here, Especially on the creature's body. I would suggest defining things in the background a little more, it's hard to tell if all that yellow is ground or water or gas or what. Adding some textures would help there. It is good you attempted a background, though, a lot of artists neglect putting backgrounds because it's so time consuming. You do however need to work on making the background equally as detailed as your subject, otherwise it seems out of place.
Lastly I will say I love the angle you used here, it's really dramatic and leaves a big impression.
This is magical. I like the colors and the more ordinary background with the crazy alien-looking creature.
Nice detail in the iris and pupil of the eye. I see that you are trying to show the roundness of the actual eyeball so points for that. I think it might have been helpful to take a look at how a round object looks in real life. I think the highlighting and shading wouldn't both go all the way around the eyeball. There would be a place where the light hits, a shadowed area and the 'in-between' shades.
I like the detail in the rest of the creature with the veins and highlighting.
I like that you have shown some distinction in the canyon but I think the lines you have there could use some fine tuning. They are a bit rough in places and there should probably be a more gradual color change in places. I think the same thing can be said for the clouds and sky. The details you used seem kind of harsh given the general lack of color gradation.
Oh, I mean the lines of the canyon stand out so much from the color of the rest of the rocks that they seem harsh. The clouds are like this against the sky but to a much lesser extent. Does that make more sense?