For alternate uniforms you must start a new game on medium. When you start to play don't collect any items (when your going to the Police station), before you get to the police station there's a path with an arch over it and when you are there, you will find a zombie. Kill him and pick up the key he has. When you go into the police station go to the dark room and use the key to get into the lockers and if you are Clair, you can get one uniform, and if you are Leon you can get two.