MengerSponge Example 1 - HyperNurbed spherical part.jpg

Did you use SceneNodes to make the sponge or classic Instance objects ?

Boy, you were fast... I was still creating the album. By now, my comments should explain it better.
No, no Scene Nodes at all, neither instances. These images were all created with my personal Menger Sponge plugin, more than ten years ago.
While the plugin also has an instance mode, this is really a single mesh in an SDS (back when it still was called Hyper NURB).
And I also thought, a Scene Nodes setup for Menger spongers could be fun...