Well, they called it a "GT Academy" theme and the DLC came out just as the American version of the show ended, so maybe it was US only.
You're not missing anything if you didn't get it anyway. Plain boring icons and a blah picture of a GT-Academy GT-R, with a bunch of stupid junk at the bottom of the screen. It looks like the cover of a game, even has the "rated T for Teen" box on it. It's supposedly dynamic, but nothing seemed to be happening when I looked at it, and only the one picture ever came up. Maybe I should try leaving it on and something will change over time, not that it will likely be any better.
If not, you could easily create a better "GT5 theme" by just putting one of your own pictures taken from the game as wallpaper on whatever icons you like.
EDIT: Sorry, it's actually "Rated E for Everyone, with Mild Lyrics." I thought Teen didn't sound right. And that is the American rating system, so if it did come out for other regions they'd probably have to make "unique version" for each of them.