You're still young, so being harsh is really not needed here. Especially since the pictures do vary in quality so one just assumes over time the better drawings will be constant. If you draw everyday it'll be ironed out Your good drawings are really good too.
Your photo ref drawings are generally good, except for the Spartans from 300 Check out some muscle photos or anatomy books for that and see how they relate. This is being nitpickey. I like the feel, and some drawings have lotsa life in them, and your faces are quite good.
I have a soft spot for hair/glam rock. So I approve of your Slash drawings