Nintendo of Japan has revealed 2 new Nintendo 3DS themes:
Pokémon Enemy Organization - Magma Gang (ポケモン 敵組織~マグマ団) and
Pokémon Enemy Organization - Aqua Gang (ポケモン 敵組織~アクア団) which are available to purchase on the eShop for 200yen each. Both themes are available on the Japanese Nintendo 3DS eShop as of December 5th, 2018.
Pokémon Enemy Organization - Magma Gang
Features: This theme features the Magma Gang and is drawn by Hitoshi Ariga. On the upper screen, Matsubusa and Kagari are featured.
Music: Pocket Monsters Omega Ruby Alpha Sapphire ~Battle! The Aqua Gang/Magma Gang's Leader ~ (戦闘!アクア団・マグマ団のリーダー)
Pokémon Enemy Organization - Aqua Gang
Features: This theme features the Aqua Gang and is drawn by Hitoshi Ariga. On the upper screen, Aogiri and Izumi are featured.
Music: Pocket Monsters Omega Ruby Alpha Sapphire ~Battle! The Aqua Gang/Magma Gang~ (ポケットモンスターオメガルビー・アルファサファイア」~戦闘!アクア団・マグマ団~)
Source:
https://www.nintendo.co.jp/hardware/3dsseries/theme/index.html