Well I at least found out that the _Other MapImg even though is KillHouse is just like the default image, they are found within the FrontEndMenus package, I've not tried to insert an image there and repack that itself since that means every custom map would have to overwrite that file
AI Teammates is not a thing in Tango Hunt anyway, I don't know if there is a way for us to get them in.
Hmm, not tried adding more points to _TangoHunt one way maybe is place them in the default map, select the new ones you want to bring over and export them as a .t3d then remove from map, open up _TangoHunt and import that .t3d.
Hell, I think even just Cutting them and Pasting them into the _TangoHunt will keep them in the current place, on that note I've noticed in the maps that come with the game the Insertion A and B PlayerStarts are kept within each game mode so they would go into _TangoHunt and not the Persistant Level, though when I was testing Multiplayer I thought I tried that and it wouldn't let anyone spawn since it said PlayerStarts where missing.
As for the Pylons I feel like the back of my memory it was best to use multiple but with the testing from the last few days I've only been using 1, might be something to look into.
I'll grab the map and toy around and see if I can find anything out