The recently certificated private pilot reported that during the flight he reduced the engine power setting and descended to an altitude of 800 to 1,000 feet above the ground so the passenger could take aerial photographs of a farm house. During a telephone interview the pilot stated that he had the power setting pulled back approximately "half way" while they were circling the farm. The pilot reported the engine seized when he attempted to apply full power to gain altitude. The airplane landed hard during an off-airport forced landing on a snow covered farm field. The airplane sustained firewall damage when the nose gear collapsed following a 75-foot-long landing roll. The pilot stated that he did not use carburetor heat while circling. Post accident inspection revealed the engine turned freely when rotated by hand and when the ignition was engaged. Examination of the spark plugs revealed they were black in color from soot. The pilot had a total of 61 hours of flight time.