When no images are provided in places that usually require an image, e.g. for a component image card, the app will create a fallback option on the fly.

Refer to the code in app/api/og/route.tsx.

In the implementation guide, a step includes changing the <svg> part of this file, so that these fallback images can be branded with your logo.

You can see examples(e.g. the Copy To Clipboad image) in the Function Overview of this website, as it is using the exact same solution.