In fact i really wanted something original.
The backward was something designed to be something like a breathing system to live in a planet exterior (if you shoot the soldier on front nothing happens to the head, but if you hit back the head, you hit the system and the soldier will die shortly).
Some sort of Metroid gameplay, turning around creatures when they attack to hit their weakpoint

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I don't mind for the model, i don't have use of it; so if you want i can just make the back of the head just simple and plain, without that volume ?
Well the model will come with colour, normal map and specular map, you 'll be free to edit them and make it very personnal like camouflage colors on clothes for example and scratches on the specular map for metal parts.
Well any variation you can imagine with a simple image editor.