Official themes can be found on that iso site but you'd still need your computer to download them. A little bit of effort is necessary in this case. If you're not willing to do that, then nope, no official themes for you.
You can install them from FBI if you grab the appropriate title key.
Warning though: When I did this, it installed over a hundred, and the theme menu can't display that many at once, you have to manually delete themes one by one until you're at something like only 28 installed. Bit of a hassle.