The site banner image is actually a specific type of infill pattern used in 3D printing called “gyroid infill”.
Generally, to save time and plastic, parts that are 3D printed are not printed as 100% solid blocks. Instead the user will set a infill percentage that defines how much of the interior space is filled. Once that is decided you still need to determine exactly how you are going to fill that space so it can be translated into commands the printer can understand.
Enter infill patterns.
Image courtsey of Cura
These are strategies used to fill in the internal space of a printed object. One of the most popular for high strengths prints is gyroid infill because it is equally strong in all directions and optimizes material use.
I think the pattern it creates also looks very interesting.
I created these images by screenshoting a layer of a print I was setting up using gyroid infill and then manipulating the image in InkScape to create a high resolution bitmap.
Thanks for your curosity!