I know I'm a few months late on this, but I thought I'd post about it for the sake that anyone might have missed it around here.
There is no news about this coming to the west yet, but if you own a Japanese 3ds, definitely give it a go.
These themes are a part of the "SEGA hard series", which you can find out more about in the following links via translator:
It's like they don't want my money! All I pretty much use my 3DS for is playing the SEGA arcade ports on it, so any of the themes would be awesome. Dat Dreamcast one, especially =3
I know right? xD As soon as I saw that Dreamcast theme, it was a must for me to download yesterday.
The crazy part is that Nintendo only charges 200 yen, which is equivalent to 1.99 USD.
Being a player of my US 3ds more than my JP version, I hope it comes to the west soon.
Basically, they don't give enough of a toss to change the Dreamcast swirl to blue in Europe, turn the Saturn black and change the name Mega Drive to Genesis in the US.
I wonder why I ever think that they'll revive classic IPs if they can't even be arsed to edit a wallpaper =P