This is a really good attempt. I'll suggest that for now, your focus shoud just be on training your eyes to see "proportions" more correctly. Make lots of line drawings with a focus on proportional accuracy. Ignore complicated stuffs like shading for now or "contrast" like most people are suggesting as that will only confuse you more. As you get better, you can incorporate other fundamemtals. Have fun!

I think you need to use loomis method for this making potrait of this photo

'Concept Art' can sometimes be such a wide umbrella that can bleed into other aspects of art (ie Illustration, Marketing Art, etc.) so I can definitely see how it can be hard to pin down specific pieces as 'Concept Art' or not. I'm definitely not the guy who can give a definitive answer for that xD, but what I can say is that your pieces do have a lot of energy, and this type of work gives me that Mad Magazine type of vibe. Good stuff! Would also be interested in seeing more of your recent work as well.