On what did Lego base the appearance of the new Hogwarts minifigs?

Question

Lego introduced minifigs based on the four founders of Hogwarts in their recent castle set:

Considering the characters have never appeared in either the movies nor the books, and knowing Lego's propensity to keep details as accurate as possible (particularly in adult sets like these) on what did Lego base the character's appearance?

(I'm obviously excluding the basic male/female attributes.)

Answer 1

Three seem to be based off the Portraits on display at The Wizarding world of Harry Potter:

Portrait of Hufflepuff: Here's where it's most obvious, as Hufflepuff is missing her braids found on Pottermore.

Portrait of Slytherin.

Gryffindor seems to be a mix of the portrait and Pottermore (as the bushy beard seems influenced by Pottermore.)

However Ravenclaw seems to be clearly based off Pottermore, as she's wearing the Diadem missing in the portrait.

H/T Brickset for pointing this out.

Answer 2

The appearance of the Lego minifigures is probably based on the illustrations in the Pottermore feature story about the Hogwarts founders:

They look fairly similar:

• Godric Gryffindor with flowing reddish hair and beard, wearing a long dark red tunic with a design up the middle and gloves (on the Lego minifigure, you can see what looks like the tunic extending onto the legs, and the hands are darker than the face suggesting gloves).
• Helga Hufflepuff, an older-looking woman (lines around the mouth) with brown, more strictly controlled, hair and yellow clothing.
• Rowena Ravenclaw, with dark hair flowing over her shoulders and wearing a long dark blue dress.
• Salazar Slytherin, bald with a beard that reaches his chest. The Lego minifigure is wearing different clothes from the Pottermore illustration, but this is probably justified artistic licence on the Lego designers' part, since green and snakes are often associated with House Slytherin.