Additional Topics

Height of clouds
Clouds are very low, if you tend to build sky towers or high builds like the Mont Saint Michel in my world. 
It is possible to change the height level of the clouds directly in the VoxeLibre game folder. But be aware, this will be overwritten with the next update ...
in mods/CORE/mcl_worlds/init.lua, line 168 set
height = mcl_worlds.layer_to_y(127),
to the level you prefer for clouds. I use a value of 188 right now.

Mapserver
Mapserver is an additional software which can easily be installed on the same server where Luanti is running. You find detailed instructions about the installation on github.
Starting the mapserver the first time will initiate the initial rendering. Depending on the size of the map, this can take some time (on my 8 GB server about 3 days ...). After the initial rendering, mapserver switches to incremental rendering: each change will be implemented in the map within a short delay.
To be able to add additional infos, as e.g. POI, train lines a.o., you should install the companion mapserver_mod. As described on the github page, you can chose between the passive and the active mode. With active mode, you have more real time data displayed on the map (number of players a.o.). To start the active mode, you have to add those lines of code into luanti.conf:
mapserver.enable_crafting = true
secure.http_mods = mapserver
mapserver.url = http://[ip of your server]:8080  <!-- e.g. 127.155.84.156:8080 -->
mapserver.key = [secret]  <!-- secret is automatically generated, to be found in mapserver.json->>
The mapserver_mod installed, you find additional blocks in your inventory:
label
POI (five colors)
Trains
To be shown on the map, you have to add those blocks in your world. There is no documentation for this mod, but a look into the mod and some experimentation allows these minimal instruction:
Train lines
Mapserver will grab all blocks and add a lines between blocks ordered by index.  Adding a station name will add a circle on the line as station symbol, click on it will open a popup with the station info. Best way will be to start at the starting station and add more or less blocks between stations. If you want to show exactly the rails, you will add more blocks, if you want just connect the stations, you put no additional blocks in between.