The pilot stated that, while en route to his destination on a night cargo flight, he experienced difficulty with the right engine which he attributed to carburetor icing. With application of manifold heat, the problem cleared up; a short while later, the right engine lost power completely. Attempts at restart were unsuccessful; the pilot declared an emergency and diverted to an alternate airport. Weather conditions in the area were bad, with a winter storm in progress; most local airports were closed due to weather. The pilot was cleared for the ILS RWY 1 approach. He reported the aircraft had iced up while en route, and that while on the ILS approach, it 'picked up more' (ice) at about 300 to 400 ft AGL. He was unable to reach the runway. Subsequently, he made an emergency landing approximately one mile short of the runway. A post-accident investigation revealed no evidence of a pre-impact mechanical malfunction of the right engine.