It was about creating three separate, different-looking worlds and also revisiting the Bene Gesserits, the age-old ones with these costumes that almost look like Egyptian mummies.

Source: https://collider.com/dune-part-2-jacqueline-west-comments/

Kevin had some sketches, and again he piled on all these reference photos of different species of turtles because basically the agenda was to make them as different-looking as possible.

Source: https://screenrant.com/tmnt-last-ronin-2-reevolution-sdcc/