To me the PR looks fine. Maybe two small comments:

• There are some functions with keyword arguments before variable positional arguments. Should we correct the order, or do we even need the *args input here?
  def plot(self, axis=None, figsize=(9, 13), *args, **kwargs)
centroids_plot.gdf.plot(ax=axis, transform=ccrs.PlateCarree(), *args, **kwargs)
self.gdf.plot(ax=axis, transform=ccrs.PlateCarree(), *args, **kwargs)

• The test functions only test whether the plot works without throwing an error, they don't test if the function plots 'correctly'. I don't know how one could improve this, just want to mention this.