It is a good thing that I have yet to buy any micro-armour - I keep thinking of different theatres to work on!
I have discussed the eastern front (Europe) previously. The western front of Europe is looking good also. One could start with 1940 France and, using virtually the same terrain, play games set in 1944 France. There is not so much variety in nationalities involved, but lots of miniatures are available.
Another theatre would be North Africa, and by this you could stretch it from Beirut or even Baghdad to Casablanca and all points in between.
And to top it all off, GHQ has started production of their Wehrmacht '47 line of what-if German vehicles - vehicles that were on the drawing boards at the end of the war. This could be used to extend any European front, but I wonder if it would work so well in North Africa...