Image img1 = new ImageIcon("img.jpg").getImage();
Image img2 = new ImageIcon("img2.jpg").getImage();

    for (int i = 0; i < 5; i++) {
        if (i % 2 == 0) {
            g.drawImage(img2, 3, 4, this);
            repaint();
        } else {
            g.drawImage(img1, 3, 4, this);
            repaint();
        }
    }