The nice thing about wargaming science fiction is that we are not limited by historical facts, but we can play these games in historical settings. The War of the Worlds movies have been set in 1900, 1955 and 2000. So we have a wide range of earthly opponents for our Martian armies.
In the late 1930s we could play WOTW against pre- and early war WWII nations. There is a series of books by Harry Turtledove that describes an attack by reptiles against humans during World War Two. Another good use for these War Machines, and substitute these Martians for the reptiles.
There is always the problem of what equipment to give the Martians, and where to get it. Rather than buy expensive sci fi vehicles, I search the Wal Marts and Dollar Tree stores for different stuff. There is always some kind of Hot Wheels, Matchbox or other vehicles that maybe after a repainting would work well for science fiction vehicles.