[x128]

Код:

uses GifImg;
...
var
  f: TMemoryStream;
  gif: TGIFImage;
begin
  f:=TMemoryStream.Create;
  gif:=TGIFImage.Create;
  try
    idHTTP1.Get('http://...../image.gif',f);
    f.Position:=0;
    gif.LoadFromStream(f);
    image1.Picture.Assign(gif);
  finally
    f.Free;
    gif.Free;
  end;
end;

если версия делфи древнее 2007 тогда: uses GifImage