Thanks to the cosprop.co.uk concept sketches, we know for certain that the vast majority of the costumes in Ever After were inspired by historical paintings, e.g., Danielle's Princess Gown, Danielle's Blue Library Gown, Jacqueline's Green Brocade Gown. We've been able to identify many of the paintings seen in these concept sketches, but since we don't have sketches for each costume, we have to speculate for some. Here is a historical painting with similar elements to young Marguerite and Jacqueline (headdresses):

Catherine of Aragon by Michel Sittow