3D images i created using a technique called Volume Displacement that uses noise to displace a volume and you can use geometry with the volume as well. These were all created and rendered in Cinema 4D using Arnold Render. 

What you are seeing is a volume with an extremely low step size of 0.2 which actually makes the volume look solid and brings out a crazy amount of detail by referencing the procedural noise.

It's an interesting method for creating more artistic and abstract 3D artwork and once it's all setup you can create endless variations and apply it onto any piece of 3D geometry. I learned this technique from Lee Griggs who pioneered this type of style. I really enjoy creating it and leaving it black and white. It makes it look haunting and mysterious.