I can't really help you to improve but i need to tell you i'm a big fan of yours characters
, specially the half dead looks like
(or maybe he's sleeping ^^ )
in the same 2e line of characters, i'm thinking you put too many light on the boobs (4th characters), because it's not plastic (same for the 5th with the white point)
Ether i don't really like the 1st
: too much "square" effect: if you want to make a robot style, you should maybe add rivet or other (or make the head like a doll)
The character with wooden katana has his left eye very bright, is it normal ?