Sets this (local) player's properties. This caches the properties in PhotonNetwork.player.customProperties. CreateRoom, JoinRoom and JoinRandomRoom will all apply your player's custom properties when you enter the room. While in a room, your properties are synced with the other players. If the Hashtable is null, the custom properties will be cleared. Custom properties are never cleared automatically, so they carry over to the next room, if you don't change them.