If you are looking for maps from the Second World War (as opposed to of the Second World War), there are a couple of sites that host worthwhile collections. One of them is the University of San Diego’s History Department. The department hosts a number of black and white maps of the time, showing various campaigns and battles. Most are in jpg format and vary in resolution. These maps comes from a variety of sources, but mostly, it seems, from the Illustrated London News that was fond of perspective views.

Indiana State University also hosts a number of maps from the Second World War. The selection is smaller and the maps are divided by theatre of war.

Many of other maps of the Second World War exist (for example), but these seemed to have been created after the fact.