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