The faceplate is attached to a rotary slider mechanism (similar to an engine conrod arrangement) which pushes the faceplate out and then lifts it up by rotating the left ear piece. Then six blue 3mm LEDs and a few resistors are attached to a 9V battery and a switch to light up the eyes which are covered with some blue lenses from an old pair of fashion sunglasses.
It's a shame I didn't take more photos during the making process but it essentially follows the same techniques used by many to make Master Chief helmets. A couple of lessons I've learnt from this are: To make a paper helmet to check scale and then make it 5-10% bigger with the cardstock as the fibreglass and body filler make the shell solid and much tighter, so much so that this helmet is really difficult to put on. At least with a bigger helmet, you can pad it out. When making the card shell, don't crease folds that don't need to be creased, otherwise you're just making more corners you need to smooth with body filler, and that's a real pain.
I also made a quick Mark II arc reactor from a used tape roll, some card, copper power wire and a ring of plastic tube. It was supposed to go together as a Zombie Iron Man, but unfortunately not many had read that series.
EDIT: Here's the link to the 405th forum where I found the pepakura file (which came from League Of Heroes). The link is also down in the comments.