BackgroundPanel.java

import java.awt.Graphics;
import java.awt.image.BufferedImage;

import javax.swing.JPanel;


public class BackgroundPanel extends JPanel{

    BufferedImage backgroundImage;
    GUIFrame window = null;

    public BackgroundPanel(BufferedImage image, GUIFrame windowFrame){
        backgroundImage = image;
        window = windowFrame;
    }

    @Override
    public void paintComponent(Graphics g){
        super.paintComponents(g);
        this.setVisible(true);

        g.drawImage(backgroundImage, 0, 0, window.getWidth(), window.getHeight(), null);
    }
}