Does anyone know of a good source for 6mm scale printable flags & banners for use in the medieval period (specifically with the Baccus Crusades Range)?  Thanks in advance!

Maverick Models have some Crusader ones in their Medieval range, among others (knightly orders, etc).

http://www.maverick-models.com/flags.htm

Edit: Just noticed that you were asking about printable ones. Sorry, don't know of any sources. Maverick do seem to have a good reputation, though, if you decide to buy some.

Thank you! Definitely looks worth checking out.

Tiny Tin troops also do some

http://www.tinytintroops.co.uk/Flags/flags_Crusades.htm

There are some Islamic ones you could scale here:

http://shedwars.blogspot.com/2015/03/saracen-pennants-flags-and-banners.html

Thanks again to all.  These look like some really solid suggestions.