public String[] imagesArray = {Images.firstImage, Images.secondImage};

String imagesPath = "/testproject/images/";
 for(int i = 0; i<imagesArray.length; i++) {
    URL imageURL = this.getClass().getResource(imagesPath+imagesArray[i]);
    ImageIcon orignalImageIcon = new ImageIcon(imageURL);
    Image newImage = orignalImageIcon.getImage().getScaledInstance(100, 90, java.awt.Image.SCALE_SMOOTH);
    ImageIcon newImageIcon = new ImageIcon(newImage);

    JButton receiptButton = new JButton(newImageIcon);
    receiptButton.setBorder((new EmptyBorder(0,0,0,0)));
    toolBar.add(receiptButton);
    add(toolBar);
    }

Bilder, die in meinem Design-Layout nicht angezeigt werden?