O q falta para a imagem aparecer

public JFrame frame;
	public float comp, alt, larg, result;
	public JLabel text_comp, text_alt, text_larg;
	public JLabel text_result = new JLabel();
	public JTextField entrada_comp = new JTextField();
	public JTextField entrada_alt = new JTextField();
	public JTextField entrada_larg = new JTextField();;
	public JButton BTN_calcular;
	public float r;

	public Principal() {
		janela();
	}

	public void janela() {
		frame = new JFrame("Cal_L");
		componentes();
		frame.setSize(350, 300);
		frame.setLocationRelativeTo(null);
		frame.setLayout(null);
		frame.getContentPane().add(new Imagens(),BorderLayout.CENTER);
		frame.setVisible(true);

	}

	public void componentes() {

		this.text_comp = new JLabel();
		this.text_comp.setBounds(14, 25, 120, 30);
		this.text_comp.setText("COMPRIMENTO");
		this.frame.add(text_comp);

		this.entrada_comp.setBounds(27, 50, 60, 30);
		this.frame.add(entrada_comp);
		//
		this.text_alt = new JLabel();
		this.text_alt.setBounds(150, 25, 120, 30);
		this.text_alt.setText("ALTURA");
		this.frame.add(text_alt);

		this.entrada_alt.setBounds(143, 50, 60, 30);
		this.frame.add(entrada_alt);
		//
		this.text_larg = new JLabel();
		this.text_larg.setBounds(255, 25, 120, 30);
		this.text_larg.setText("LARGURA");
		this.frame.add(text_larg);

		this.entrada_larg.setBounds(252, 50, 60, 30);
		this.frame.add(entrada_larg);
		//
		this.BTN_calcular = new JButton("Calcular");
		this.BTN_calcular.setBounds(120, 120, 100, 50);

		BTN_calcular.addActionListener(new ActionListener() {

			@Override
			public void actionPerformed(ActionEvent e) {

				calculos();
			}
		});

		this.frame.add(BTN_calcular);
		text_result.setBounds(150, 180, 100, 50);
		frame.add(text_result);
		//

	}

	public void calculos() {
		this.comp = Float.parseFloat(entrada_comp.getText());
		this.larg = Float.parseFloat(entrada_larg.getText());
		this.alt = Float.parseFloat(entrada_alt.getText());

		r = (comp * larg * alt) / 1000;

		text_result.setText("" + r);

	}

	public static void main(String[] args) {

		Principal p = new Principal();

	}

	public class Imagens extends JPanel{
		
		public BufferedImage imageL; 
		
		public void metodoImagem(){
			try {
				imageL = ImageIO.read(getClass().getResource("aquario.gif"));
			} catch (IOException e) {
				e.printStackTrace();
			}
			repaint();
		}
		
		public void paint(Graphics g) {
			g.drawImage(imageL, 100, 100, null);
			g.dispose();
		}

	}
}