The Krigsspll.dk site offers a very large selection of downloadable flags for the Crusades. They are all very well done.
The New York Public Library Systems Digital Library has digitized images of thousands of plates, prints and paintings, including these of the uniforms of Byzantium through 1453.
The Fanaticus Site has a set of Crusader banners for you to download and print. They’re in 15mm scale.
Kurtis Brown offers a one-page painting guide to Vikings.
Early Blazon offers illustrations of hundreds of coats of arms through the Crusades.