Top three I have taken for granted for being source of really high quality maps (Some of them I cant even open as my PC freezes, regarding 400MB+ and 20 000 res images)
David Rumsey Historical Map Collection http://www.davidrumsey.com/
List of Online Digital Quality-accurate maps http://www.oldmapsonline.org/about/
World Digital Library http://www.wdl.org/en/
I do not know much about other countries, but as estonian I have access to Estonia National Archives, which offer to countless number of historical maps related to Estonia and its history. I imagine the number of people who are not even aware of access they actually have, they never used, or did/do not know about. Just need to do a little homework. Plus every higher educational student should have access to hundreds of databases, one some of them offer image/pictural support-sources - mostly regarding the accurate Battle plans, fronts that some Mapmakers try to imitate here.
The problem is not, that Warlight community would lack the source of maps or accces to them. Rather incapability to google or search particual map from database. Even google image support is enormous and offer quite high resolution needed for Vector drawing.
This is the decade of Free access to information - and I am glad to hear that it is expanding. So make the best of them.