Commentary:

As I have said in the "Angry Birds Stella: Stella's Hobby Book" page, sorry for the poor quality photos in the PDF. Would've been able to present something higher quality if I hadn't let sloth get the better of me.

Anyways, like Stella's Hobby Book, there are 4 pieces of artwork made specifically for this book. Unlike Stella's Hobby Book, only 2 of these artworks have been uploaded to Behance by the artist Diana Egea, the other 2 pieces don't seem to have been uploaded anywhere. So until I miraculously get my hands on a higher quality pdf of this book, these shitty photos I took are the only online traces of Gale's Marie Antoinette and Catherine The Great outfits.

Actually, the lineart for the Marie Antoinette outfit (sans paper fan) was reused for page 21 of "Angry Birds Stella Diaries: Gale Has a Ball", so there's that.

Pages 12-17 could also provide some inspiration for clothing if you intend on doing anthro/gjinka designs of the Stella cast, as it contains a quiz about clothing styles, with each questions having 6 options, each associated with one of the six characters!
...Except Luca. He has 0 swag on account of being 0-years old, so Gale gets to hog two options per question instead. Her greed sickens me.

Also, I may have accidentally duplicated page 20 and 21 in the PDF. Hope you don't mind, because I don't have a free PDF editor on my computer. :P