Herro! I am an amateur as well. I'll see what I can point out.
With Samus I'd say she looks a little off balance; like she is going to fall backwards. I'd try and pull her right leg under her body some more and change it from a profile view to more of a 3/4ths view. The helmet looks a bit out of place. It is smooth and the the rest of the armor looks grittier(because of the dithering). Also I don't think the red you chose goes well with the orange but it may be just because of the difference in textures.
* PioneerToTheFalls
's at the bananas.
That is a funny idea. You could probably stand to tone down the dithering on those as well. It makes the bananas look more cylindrical when they should have ridges.
The grenade also looks cylindrical. The vertical lines are bent and come together at either end so it looks like they are wrapping around the grenade. You didn't do this with the horizontal lines so it only appears to be curved in one direct.
In regards to the shiny orb, I'd say you need to remove the grittiness. For an object to reflect a beam that sharp it'd have to be pretty smooth. Also the size of the streak is too large for a sphere. When you shine a light on an object, the area the reflects the brightest is the area the is best angled to direct the light into your eye. (Gah! That is hard for me to word for some reason. Hopefully you understand.) So essentially what you are showing, with that large streak of white, is that the surface it is bouncing off of is flat(because it is solid white). It also says it is perfectly aligned with your eye( because it is such a large mass of white) :\. Since that is clearly not the case, it ruins the 3d illusion that you were going for.
With all that said; keep up the the good work!
The Metroid and several of the guns look pretty sweet. If it wasn't for the few problems with Samus I'd include her as well.