At
https://area51.xcomufo.com/depot2.htm there are a lot of maps
I open some of them with MapView and them appear usable
I think that some could be used as is when a Map Maker adds the missing map routers
(such as Normandy, Native, New Farm)
Terrains named
Siberia,
Storm Mountain and
SandCastle are underground base.
They could be used for ufo base mission or for an other type of mission
an idea could be "Man in Black base mission"
There are some urban terrains too but I think that there is one possibility thet Civillian uses them already
After that the are some terrains that use TFTD palette, I am studing to use them in some way.