Your drawing skills seem pretty decent. The main area I see needing work is lighting from imagination. You seem to do it a good job copying the shadow shapes from the models, but when you shade in your original work, you are shading the micro shapes of the muscles but not the overall shape of the arm (a cylinder). So maybe drawing white cylinders under various lighting scenarios would help. The other critique I have is about the body of work as a whole: I can't tell what you want to do. Figurative fine art? Illustration? Concept art? Caricature? It's fine if this is a hobby, but if you're aiming to go pro in the future, I think you need to get a clearer idea of what you want to get hired for, and tailor your portfolio to that.

cool stuff!

Hey Alex! You're doing great! I like the warrior guy :)

Hi Alex! Just wanted to say great work! Keep at it man!