Nintendo Japan has revealed 3 new Pokémon Nintendo 3DS themes: Pokémon Peeking Friends (ポケモン ぴょっこりフレンズ), Pokémon Traditional Japanese Pattern 'Poké Crests' and 'Kokeshi Dolls' (ポケモン 和柄 ～「ポケ紋」と「こけし」) and Pokémon Poké Kyun Collection (ポケモン ポケキュンコレクション). These themes cost 200yen each and are available for purchase as of December 22nd, 2015 on the Nintendo 3DS eShop store.

Pokémon Peeking Friends (ポケモン ぴょっこりフレンズ)

Features: "Pyokkori" Pokémon have very cute faces in this theme. The lower screen includes the fan favorites Pikachu and Eevee heads peaking out on a panoramic wallpaper. The upper screen features the Pokémon from behind and is designed to be charming.
Music: BW - Dress Up with Props (グッズでドレスアップ)

Pokémon Traditional Japanese Pattern 'Poké Crests' and 'Kokeshi Dolls' (ポケモン 和柄 ～「ポケ紋」と「こけし」)

Features: This Japanese-style theme is decorated with Pokémon that have become Kokeshi dolls as well as Pokémon Crests. When the user slides, the Pokémon Kokeshi dolls on the bottom screen will sway back and forth.
Music: XY - Restaurant Rolling Dreamer (レストラン ローリングドリーマー)

Pokémon Poké Kyun Collection (ポケモン ポケキュンコレクション)

Features: From the Pokémon Card Game XY BREAK Concept Pack, this cute "Poké Kyun Collection" theme has appeared ♪
Music: XY - Friends' Theme "We Meet Again!" (ともだちのテーマ「また会えたね！」)

Sources: https://www.nintendo.co.jp/3ds/theme/list/03042/index.html, https://www.nintendo.co.jp/3ds/theme/list/03043/index.html and https://www.nintendo.co.jp/3ds/theme/list/03042/index.html