Almost every one I've seen has taken cues from the History of Costume by Braun & Schneider, a collection of Victorian plates printed in German between 1861 and 1880. Do a Google search on 'Costume History' and this is the first site that will appear. Though the people who have made it available online do specify that "One must be aware... that these illustrations have a Victorian perspective to their designs," they also state that "This book is an excellent source for students who are studying the history of fashion and for costume designers."
No, it isn't... at least not in every illustration on every page. It might be an excellent source for students studying the changing perception of costume history and the ways in which modern tastes and conventions influence our interpretation. But some errors are pretty glaring in light of more recent research.
Let's start with the 4th century Teutons. According to Selkie, our resident historian, most of the information here might still fit with archeological findings, though the theories on this early garb have changed. But there are some probable errors: the tunics with short sleeves, not long sleeves; the chainmail shirt with no sleeves, when it ought to have short sleeves; and those spirals over the boobs. There is no evidence for boobiespirals. Also, what's up with the kid? Belt and fur lining, fine. But straps over the shoulders? No undershirt? Have we got an infant Conan the Barbarian here?