Dima:

Thomas gave you some really good information to help you understand your
problem.  In addition here is a simple program that you can compile and
run to see how the ImageObserver works.  Notice when you run it how many
times paint() is called.  It can be 10s or 100s of times while the image
is being prepared.  While I didn't include it in this example you can
use the checkImage() to get some information about the drawing status of
your image.  In most cases however it isn't required.

import java.awt.*;
import java.awt.event.*;
import java.net.*;

public class ImageObserverExample extends Panel {
    Image image;
    String msg = "Loading Image";
    int n;

    public ImageObserverExample() {
        try {
            URL url = new URL(
             "http://www.thealpacastore.com/alpacacam/latest640.jpg");
            Toolkit toolkit = Toolkit.getDefaultToolkit();
            // use createImage instead of getImage - see api docs for why
            image = toolkit.createImage(url);
        } catch (MalformedURLException murle) {
            msg = "MalformedURLException";
        }

        setPreferredSize(new Dimension(400,300));
    }

    public void paint(Graphics g) {
        // show the number of calls to paint()
        System.out.println(++n);
        // if there is an image and drawing has not finished
        // note: if the image is null drawImage will return true
        if (image == null ||
         !g.drawImage(image,0,0,getWidth(),getHeight(),this)) {
            // draw the message
            g.drawString(msg,20,getHeight()/2);
            System.out.println(msg);
         }
    }

    public static void main(String[] args) {
        Frame frame = new Frame("ImageObserverExample");
        frame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent we) {
                System.exit(0);
            }
        });
        ImageObserverExample examp = new ImageObserverExample();
        frame.add(examp,BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
    }
}