From Beowulf on the Norse mythology has been Christianized and so the Valkyries were likened to angles. In reality the Valkyries image came from the crows and ravens who descended on the battlefields. The helmet is inspired.
Take this with a grain of salt! This piece represents the best I could ever get out of Firefly. It has got some real problems! I switched over to Povray a long time ago. Most of the pieces in my gallery was rendered with Povray.