You've already created an ImageIcon. You can retrieve an Image from it. That Image can be drawn on the Graphics object.
Note however that you shouldn't load the ImageIcon each time paint or paintComponent is invoked. This could occur many times a second, and you don't want all that I/O all the time. You should create the ImageIcon in the constructor and assign it (or its Image) to an instance field, and use that instance field when painting.