The Krigsspll.dk site offers a very large selection of downloadable flags for the Crusades. They are all very well done.
The Krigsspil site has a large number of downloadable flag images for the American Revolution. The flags are all in .jpg format, so they can be resized to fit whatever figures you use.
Here’s a selection of early crusader period flags.
The Project Auldearn 1645 blog has a nicely researched and presented set of flags for the Scottish end of the English Civil War. Just download and print.
Krigsspil has a large selection of flags for the American Revolution, free for the downloadng