galera como posso adicionar 2 imagens diferentes, 1 para cada JPanel nessa aplicação?
public class Principal {
	private JFrame frame;
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					Principal window = new Principal();
					window.frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}
	public Principal() {
		initialize();
	}
	
	private void initialize() {
		frame = new JFrame();
		frame.setBounds(100, 100, 450, 300);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.getContentPane().setLayout(null);
		
		JPanel panel = new JPanel();
		panel.setBounds(23, 21, 158, 203);
		frame.getContentPane().add(panel);
		
		JPanel panel_1 = new JPanel();
		panel_1.setBounds(191, 21, 158, 203);
		frame.getContentPane().add(panel_1);
	}
}