To add new maps to your server you will need to edit your Game.ini, on our platform you will find this here: /home/container/Pavlov/Saved/Config/LinuxServer/
Available game modes as of 9/1/2021: SND, TDM, DM, GUN, ZWV, WW2GUN, TANKTDM, KOTH (TTT - Shack Only)
Maps running a Custom Game Mode (TTT (on PC), BR, Duel, etc.) don't care which GameMode you chose, as long as it isn't Shack TTT, which will always override.
UGC###### are for custom maps from steam workshop (PC Only). Find the map you want in the workshop. This is the URL for Mirage (https://steamcommunity.com/sharedfiles/filedetails/?id=1661803933). To put Mirage in your rotation UGC1661803933 would be the correct MapId
For example it would look like this: