Military pushups are a good modification for regular pushups. They provide more resistance for your arms and chest, and give you more results in strength and fitness. To go from a normal pushup to a military pushup, simply move your arms inward from shoulder length apart to less than shoulder width. Then do pushups like normal.
To improve the appearance of your shoulders, you should use weights. Dumbbells are great for shoulder exercises like push presses and lateral raises. Presses with barbells can also yield very good results. Using weights will build up the muscles in your shoulders and give them a more toned appearance. For the best results, be sure to lift weights at least twice a week.