create your own class extending Canvas3D.
This is one I wrote for 2D text be displayed over 3d canvas. should work with images.
import javax.swing.*;
import java.awt.*;
import com.sun.j3d.utils.universe.*;
import com.sun.j3d.utils.geometry.*;
import javax.media.j3d.*;
import javax.vecmath.*;
import com.sun.j3d.utils.image.*;
import javax.media.j3d.LineAttributes;
public class JoCanvas extends Canvas3D
{
private String t;
private Font f;
public JoCanvas(GraphicsConfiguration gcIn)
{
super(gcIn);
f = new Font("Arial",0,30);
t=" ";
}
public void postRender()
{
J3DGraphics2D g = getGraphics2D();
g.setFont(f);
g.setColor(Color.orange);
g.drawString(t, 100, 100);
g.flush(true);
}
public void setText(String s)
{
t=s;
repaint();
}
}