App Screenshot Creator makes App Store and Google Play screenshots from ready-made templates. Add your own app screens, then customize fonts, sizes, colors and alignment, and build several screenshots in one project. The page lists 20 templates and PNG and JPG export.
The free plan covers 3 projects with basic templates and single-size PNG export. Pro is a $29 one-time payment for unlimited projects, all premium templates and multi-size export in PNG and JPG. A separate free device mockup generator (iPhone, iPad, Pixel and Galaxy frames) runs in the browser without an account.
The builder wanted app developers to be able to produce polished, store-ready screenshots quickly, without design software or a designer.