Dude, the death trooper piece is teh roxorz, but...
...the way his thing is sticking out of his breast plate, it's just not natural man! lol
But nice none-the-less.
I would recommend sketching real people now. You're at the point most artists get to where they're decent, but in order to improve, they actualy have to look at the real thing.
I started sketching my hand in different positions, and my family's heads.
It takes a while, but it's fun and you get to show off later. :-D