Use image as backgroung of form

Use standard method of Form component (Brush method). This method has Bitmap method, which allows you to fill background of the form by images.

procedure TForm1.FormCreate(Sender: TObject);
var
  MyBitmap: TBitmap;
begin
  MyBitmap:=TBitmap.Create;
  MyBitmap.LoadFromFile('factory.bmp');
  Form1.Brush.Bitmap:=MyBitmap;
end;