Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

function TileImage(const FileName: TFileName; Sender: TObject): Boolean;
 var
   x, y: Integer;
   Bmp:  TBitmap;
 begin
   if FileExists(FileName) then
   begin
     bmp := TBitmap.Create;
     try
       bmp.LoadFromFile(FileName);
       with (Sender as TImage) do
       begin
         for x := 0 to (Width div bmp.Width) do
           for y := 0 to (Height div bmp.Height) do
             Canvas.Draw(x * bmp.Width, y * bmp.Height, bmp);
       end;
     finally
       bmp.Free;
     end;
     Result := True;
   end
   else
     Result := False;
 end;

 procedure TForm1.Button1Click(Sender: TObject);
 begin
   if Opendialog1.Execute then
     TileImage(OpenDialog1.FileName, Image1);
 end;