Map Provider : CustomURL

Hi,
Do you have information on how to use the CustomURL Feature for Map Provider ?

on both latest stable and daily (5/16/2022) versions there is a option in Application Settings / General / Miscellaneous / Map Provider to select CustomURL, but I can’t find information on where to setup the url, and what systems are supported.

My main goal is to provide a map of a simulated world and was hopping to use either a high resolution image of the map or use an open source GIS.

image

In case someone bump into the same issue. the parameters can be set offline map / options