If you are after maps you could do worse than the computer game ARMA 3.
It's got a built in editor for creating missions so you can pan the camera around the huge maps, many are a few hundred square kms, zoom in to the desired level and then take a screenshot to use.
Here's one I did in a few minutes
Or zoomed in a bit more after adding two wrecked vehicles and a ruined house.
You can even grab some angled shots to give your players a bit more of a feel for the area.
The base game has a Greek island for it's map but there are many free European maps available through the Steam workshop.
The images above were from the Global Mobilisation DLC a purchased extra.
If you think this is a good idea it's currently on sale on Steam.