Self-explanatory title. Personally, I think a "Colonization of North America" map might be interesting, with colonial England, France, Spain, Portugal, along with Native American empires and powers, like the Aztecs, Incans, Narragansetts, Pequots, &c. So far as I know, there's nothing like that up yet. What else would you like to see? Maybe we'll get some good ideas.
I've always thought a city might make for a good battlefield. Or maybe a college campus, even. Zoom in very deeply, and individual buildings and roads are territories. If there aren't a lot of rivers and lakes, maybe split units into infantry and tanks. Tanks can't enter buildings, but infantry all has agoraphobia, so they stick to the buildings, and only cross the roads when a tank helps them across. Or something.
I would love to see a version for the wars of the Roses... Not just Lancaster v York but the powerful noble houses fighting for supremacy, Nevilles, vs De Veres vs Plantaganet, Beaufort etc. This would be different in that the nobles had strengths in different parts. For instance, the De Mowbrays had strongholds in Norfolk, Yorkshire and North wales and the Nevilles in Yorkshire, South Wales and the midlands...