procedure TForm1.Button1Click(Sender: TObject); 
var 
  li: Word; 
begin 
  // Loop through all images of a TWebbrowser 
  // Schleife ьber alle Bilder im Webbrowser 

  for li := 0 to WebBrowser1.OleObject.Document.Images.Length - 1 do 
    // Exchange image with an own image 
    // Austauschen der Bilder im webbrowser - durch 'MyImage.gif' 
    WebBrowser1.OleObject.Document.Images.Item(0).Src := 'c:\MyImage.gif'; 
end;