I am trying to set background image width 100, height 100 and making the border to null.
So that i can design the input field looking similar to following, but border is not applying and round corner does not exit + there is no background image apply way around.

// Current
String[] petStringsa = { "eth0: ", "eth1: " };
JPanel namePanela = new JPanel(new BorderLayout());
JLabel nameLabela = new JLabel("View Inerfaces: ");
nameLabela.setDisplayedMnemonic(KeyEvent.VK_N);
final JComboBox nameTextFielda = new JComboBox(petStringsa);
nameTextFielda.setBorder(null);
nameTextFielda.setBackground(Color.white);
nameLabela.setLabelFor(nameTextFielda);
namePanela.add(nameLabela, BorderLayout.WEST);
namePanela.add(nameTextFielda, BorderLayout.CENTER);
Take a look on this resource http://java.sun.com/developer/technicalArticles/GUI/translucent_shaped_windows/
I explains how to change the swing elements’ shape.
This thread explains how to put background image: How to set an image as a background for Frame in Swing GUI of java?
Although my answer almost duplicates the Hovercraft Full Of Eels’ comment I decided to write it because it contains specific links.