Hey i am a newbie too, so take what i say with a grain of salt ^^ I like your character and design. it is really nice. But i agree with the others, that you should perhaps try and push the contrasts even more. And even add a bit of hue shifting. (for instance here i used a reddish color for shading the orange suit)
I did a quick paintover to give you an idea of what you could do. I would also advice to stay away from 100% black and white, and instead use a dark and light grey.

Waaaaah wut have you done!!. hah im kidding. thanks for the advice my fellow newby. I gotta admit though hue shifting seems so alien to me since i'm not well knowledgeable on color theory, but i will have to look into it. i like your variation of the helmet highlights. i was too picky and couldn't find a reference for the life of me so i picked a random light direction and went there, but i like where you went with it even more. This inspires me. i'll have to update after i get home. thanks again.

Jesia gave you good advices, I will add that you should stay away from pillow shading and using too many similar color tones to achieve smooth transition cause it only makes it blurry. You can read about pillow shading and other useful stuff here http://www.pixeljoint.com/forum/forum_posts.asp?TID=11299

Also, his left arm is shorter than the right one, and belt is a bit too loose.

ill take note of your advice too, thanks in advance.. or in present. Ill have to work on it some more when i get home.

I like your sprite so far. You need higher contrast between colors, especially in the helmet cause your black, dark blue and gray are to similar, so it's hard to read. Those brown spots on the legs are not symmetrical, one is on the side of his right leg and second one is almost on the front of his left leg. By removing second one you will still preserve concept detail, and you'll solve the problem.

About layers, as rikfuzz said it's not a problem if you don't use different opacity layer which will generate additional colors (again this can be tweaked in final image so it's not so big problem). If it helps you use it, people use it for animations regularly.

Alright i made some adjustments. Not necessarily good adjustments though, because i need to work on color theory.