When I test the nearby feature locally everything seems to work. But when I look closely, the image URL used for the pins is set to the mapbox default configured in the mapbox-lib.js.
e.g.: //api.tiles.mapbox.com/mapbox.js/v3.3.1/images/marker-icon.png
Normally this is set to an asset path from the Maps (Kartographer) extension [1]. But that does not seem to work in this case.