Como colocar uma imagem background no netBeans. JAva SE

seuFrame.setBackgroundImage(new Image("./images/seupng.png"));

JLabel background = new JLabel(new javax.swing.ImageIcon(getClass().getResource("img/suaImagem.png")));

public class JSeuPainel extends JPanel   
{   
  
    Image im = new ImageIcon ( getClass ( ).getResource ( "/fundo.png" ) ).getImage ( );   ---- sua imagem
  
    public void paintComponent ( Graphics g )   
    {   
        super.paintComponent ( g );   
        int x = ( this.getWidth ( ) - im.getWidth ( null ) ) / 2;   
        int y = ( this.getHeight ( ) - im.getHeight ( null ) ) / 2;   
        g.drawImage ( im , x , y , this );   
    }   
  
}