My idea. I admit it might need a little work.
Manifest Destiny
Many countries believed it was their god-given right to expand.
Create a map showing a country with this belief that it is destined to expand and grow, and uses it to justify its own aggressive imperialist expansion.
It could be a country that never expanded (much) in OTL, or one that did, but if so in this world does in another direction.
Examples:
An Australian state decides it is destined to rule Indonesia.
The founding fathers of the USA decide to concentrate on liberating Canada before expanding west.
The Tsar chooses to ignore the Siberian wastelands to the east and instead concentrates on expanding into Poland. Or Scandinavia. Or Turkey.
The rulers of Sweden/Poland/Ottoman Empire decide to do the opposite.
Note this should not just be
Germany wants to expand into Belgium to get acces to the Channel Ports. The nation must have a deep, ingrained belief it is
destined to expand in this way (see
http://en.wikipedia.org/wiki/Manifest_Destiny), therefore it would probably be pre-1900.
Lebensraum I suppose would be the exception, but if you were making a map of Germany it would have to expand West or North or South rather than East as it did IOTL.