On Server List Ping

Syntaxes	Version
server [list] ping	2.3

Called when a server list ping is coming in, generally when a Minecraft client pings the server to show its information in the server list. The IP expression can be used to get the IP adress of the pinger. This event can be cancelled on PaperSpigot 1.12.2+ only and this means the player will see the server as offline (but still can join). Also you can use MOTD, Max Players, Online Players Count, Protocol Version, Version String, Hover List and Server Icon expressions, and Player Info Visibility and Hide Player from Server List effects to modify the server list.

Exemple:

on server list ping:
    set the motd to "Welcome %{player-by-IP::%ip%}%! Join now!" if {player-by-IP::%ip%} is set, else "Join now!"
    set the fake max players count to (online players count + 1)
    set the shown icon to a random server icon out of {server-icons::*}