Reinkstone is an app designed by the Reinkstone team for Reink Case, enabling users to customize wallpaper for their phone case's e-ink screen. Users can create personalized wallpapers by editing text and images or choose from a variety of official themes. These wallpapers can then be transferred to the e-ink screen of the Reink Case for display.

The app offers built-in theme wallpapers like memes, copywriting, and cartoon portraits, as well as the ability to create exclusive dynamic wallpapers using favorite pictures and text. Users have full control over font, color, direction, and size settings to craft unique wallpapers. Additionally, the app supports displaying QR codes on the e-ink screen for easy sharing.