Nintendo has added a Pokémon: Let's Go, Pikachu! / Pokémon: Let's Go, Eevee! wallpaper for PC, smart phone, or tablet to their My Nintendo rewards program. The wallpaper costs 50 Platinum Points to redeem.

Reward info

My Nintendo members! Redeem your points to get a new wallpaper for your smartphone and PC featuring the stars of the new Pokémon™: Let's Go, Pikachu! and Pokémon™: Let's Go, Eevee! games.

It can be downloaded in eleven different resolutions for PC, smart phone, or tablet.

Available sizes
Landscape format:
3840x2160・ 2560x1440・1920x1080・1366x768・1280x1024

Portrait format:
(Pikachu): 1440x2560・1242x2208・1080x1920・750x1334・720x1280・640x1136
(Eevee): 1440x2560・1242x2208・1080x1920・750x1334・720x1280・640x1136

Sources: https://my.nintendo.com/news/4202158adf9cead2 and https://my.nintendo.com/rewards/73fb4ffe323b3797