Using a for-loop to fill 20 picturebox number 'i' with image
Assuming you have a container for each of your PictureBox controls do the following:

Use a List control:

  List&lt;PictureBox&gt; boxes = new List&lt;PictureBox&gt;();


Search for your picture boxes:

  foreach (Control c in YourContainerName.Controls)
  {
    if (c is PictureBox)
    {
      boxes.Add(c);
    }
  }


Then in your method:

public void afficheuneimagecombo()
{
  foreach (PictureBox pb in boxes)
  {
    Item imguse = new Item();
    pb.Load(imguse.getImage());
    pb.SizeMode = PictureBoxSizeMode.StretchImage;
  }
}