So far, they are all a great start. Since I am a stickler for accuracy, I would probably end up modifying them in the following ways if you didn't:
Handplate: Shape is pretty good, could be a little higher resolution to match the curviness in the pictures. Also, you have the slots reversed, they should be raised, not sunk in(see:
blue w/ assault rifle).
Kneepad: Shape looks good again and resolution is high, however it is more conical in the screenshots(see:
red vs. blue pvp) with the tabs flaring out more. You also have the triangle normals flipped the wrong way, but Pepakura Designer can fix that on import.
Shoulderpad: Geometry is okay. Shape is a bit off. Needs to curve a lot more around the shoulder at a higher angle(see:
blue w/ assault rifle). The notch at the top should be curved instead of pointed(see:
blue and tan w/ battle rifle and
blue vs. promethean). The details at the bottom could be adjusted a bit too(see:
red w/ blue exploding). Also, half the geometry has the normals flipped, which can't be fixed with Pepakura Designer.
Can you tell me where you found this image? I am currently working on the helmet on the far right(I am calling it Demon, like the demon masks samurai used to wear).