Just a little something I cooked up from a freebie armor that I found by Royloo over at poseraddicts.com. I thought it looked quite Helghasty. Technological advancements allowed for the miniaturization of the breathing apparatus so that it fits entirely into the face mask now and uses nano-tech to manufacture breathable gasses from raw elements found in the outer atmospheres of most known worlds. Storage cells in the suits back pack store breathable gasses in pressurized cells for use when the Helghast have to go into environments that have no raw materials from which to manufacture breathable gasses.
I'm not really familiar with Killzone, but based on a quick google search I agree that this armour looks quite Helghasty. Pretty cool pic too, nice work on the pose. Seems to be missing a shadow, though...