Now, with a true map campaign, the map becomes very important because it's actually the details on the map that effect the campaign. They're the details that let you know which areas are urban, which are grassland, which are impassible seas or rivers. So, with a true map campaign, the devil really is in the detail, and the more detailed your map, the more detailed the campaign.
What you use for the map is down to you, it can be as simple as a sheet of A4 with some woods, rivers, mountains and cities drawn on it, or it could be a genuine map from the real world adapted for a futuristic campaign.
You could use an ordinance survey map to represent a region or a map of a medieval city to represent an urban area for a cityfight campaign. As long as the map suits your purpose and is clearly understandable, it's fine. So with this in mind, it's well worth taking your time to find the right map to fit your campaign as it really is the most important part of planning your map campaign.
City street plan map
Ordnance Survey map
Medieval city map