Although the Headless Server does not deliver catalog data, it still needs an underlying commerce connection to resolve page grids inherited along the commerce category hierarchy, extend the commerce navigation and provide dynamic product lists managed in Studio. Therefore a running Commerce Hub is required. In addition, at least one properly configured Commerce Adapter is required in the Headless Server app.

Depending on your system setup, this may be any combination of

commerce.hub.data.endpoints.sfcc
commerce.hub.data.endpoints.hybris
commerce.hub.data.endpoints.commercetools
commerce.hub.data.endpoints.wcs

For catalog image URLs, a site mapping has to be configured in the same way as for the CAE, for instance