There's no need to replace the Leaflet package. You can just change the tiles provider from `'Stamen.Toner'` to something else. Take a look at [leaflet-providers](https://github.com/leaflet-extras/leaflet-providers) on how to do this. MapBox requires registration (the lab doesn't have an account, feel free to create one), but maybe try registration-free providers before? You can [preview](http://leaflet-extras.github.io/leaflet-providers/preview/index.html) them, and some seem promising. `'OpenStreetMap.HOT'` looks pretty sweet. :-)