In Java, every time I add a few pieces to JPanel, the second thing is not created?

I create a JPanel and add some simple buttons with listeners attached to them. Then I decided to add an image to the background of my panel, so I switched JPanel to ImagePanel. The buttons worked on JPanel, but now that I have added a bunch of code to display the background image, the buttons no longer appear. I have not changed any buttons with the addition of code, so I am very confused about why the buttons are no longer displayed. This also happened in my separate GameFrame class. I added 2 rectangle panels to the panel, then 3 buttons. Only buttons are displayed for this panel, although the rectangles work before the buttons were added. Can I have only one JComponent type per panel or something else? I really don't understand why he does it. Thank you for your time.

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class TitleFrame extends JFrame
{
    private ImagePanel panel;
    private JButton mage;
    private JButton rogue;
    private JButton warrior;
    private Image image;

    public TitleFrame()
    {
        JFrame frame = new JFrame();

        frame.setSize(1024, 768);
        frame.setTitle("Title Screen");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);

        createMageButton();
        createRogueButton();
        createWarriorButton();
        ImagePanel panel = new ImagePanel(new ImageIcon("C:/Users/Derek Reitz/Documents/Eclipse Projects/GameApp/src/background.jpg").getImage());
        panel.add(mage);
        panel.add(rogue);
        panel.add(warrior);
        panel.paintComponent(frame.getGraphics());
        frame.getContentPane().add(panel);
    }

    private void createRogueButton() {
        rogue = new JButton("Select Rogue");

        class AddButtonListener implements ActionListener
        {
            public void actionPerformed(ActionEvent event)
            {
                moveToNextFrame('r');
            }
        }

        ActionListener listener = new AddButtonListener();
        rogue.addActionListener(listener);
    }

    private void createWarriorButton() {
        warrior = new JButton("Select Warrior");

        class AddButtonListener implements ActionListener
        {
            public void actionPerformed(ActionEvent event)
            {
                moveToNextFrame('w');
            }

        }

        ActionListener listener = new AddButtonListener();
        warrior.addActionListener(listener);
    }

    private void createMageButton() {
        mage = new JButton("Select Mage");

        class AddButtonListener implements ActionListener
        {
            public void actionPerformed(ActionEvent event)
            {
                moveToNextFrame('m');
            }
        }

        ActionListener listener = new AddButtonListener();
        mage.addActionListener(listener);
    }

    public void moveToNextFrame(char c) 
    {
        GameFrame game = new GameFrame(c);
    }

    class ImagePanel extends JPanel 
    {

        private Image img;

        public ImagePanel(Image img) {
            this.img = img;
            Dimension size = new Dimension(img.getWidth(null), img.getHeight(null));
            setPreferredSize(size);
            setMinimumSize(size);
            setMaximumSize(size);
            setSize(size);
            setLayout(null);
        }

        public void paintComponent(Graphics g) {
            g.drawImage(img, 0, 0, null);
        }

    }
}