2D Graphics and image won't show correctly

Question

First of all, I have two class' GameGUI and paintCircle

In paintCircle I'm drawing my circle on top of my JPanel image from GameGUI, but with the standard grey-ish background

• I only want the circle to show, what am I missing? I've been through all the different settings without any luck.

The same goes for when I've tried to put in a new image of a triangle (.PNG-file), how do I only make the triangle visible or even change its size?

public void paintComponent(Graphics g){
        Graphics2D g2d = (Graphics2D) g;

        Ellipse2D.Double e = new Ellipse2D.Double(200,200,200,200);
        g2d.setColor(Color.red);
        g2d.fill(e);
        }