This beautiful heraldry link has categorised links from 1291 to the sixteenth century. The two images below are the ones most relevant to crest building in the mid fifteenth century.
http://www.historyupclose.com/images/heraldry%20images/15thC-late.jpg
I don't know where this comes from (document or country). It is stylistically similar to other 15th C examples.
http://www.historyupclose.com/images/heraldry%20images/15thC-late_Hyghalmen-Roll-of-arms.jpg
More mantling with animal, human and object models rising from the helm.
