David Eldersveld shows off how you can customize maps in the Power BI Report Builder Map Gallery:
One of the defining features of Power BI’s [paginated] Report Builder vs the current geospatial offerings in Power BI Desktop is the native support for ESRI Shapefiles. If you have worked with maps in Report Builder over the years, you may have used the Map Gallery. The Map Gallery offers a collection of built-in geographies, but you can also customize and enhance what’s available out of the box.
David takes us through an example of simplifying one map, but the same technique can help in other ways.