The official Japanese website has announced that new C-Gear and Zukan Skins for the Japanese versions of Pocket Monsters Black and White will be distributed on the Pokémon Global Link website. The fully evolved forms of the Kanto starters: Fushigibana, Lizardon and Kamex are the featured C-Gear downloads while the Zukan skin features the actual Kanto starters. The Zukan skin comes in two colors: Red and Pink. The skins will be available from February 25th, 2011 at 17：00 JST until April 25th, 2011 at 23：59 JST. The skins will be available to all players that have an account.


Our C-Gear page has been updated with the latest skins.


Source: http://www.pokemon-sp.jp/news-sp/2011/02/0218_01.html

Got a question regarding the C-Gear wallpapers. Is there some sort of fan-submitted wallpapers, or only official wallpapers can be used?
It could be nice if you could design/upload your own wallpaper, then use it in your game.

They are official ones only. They might have a contest at some point to let people submit fanart but you're guess is as good as mine.