Software: Illustrator CC
Background images are sort of boring. In many cases that are boring on purpose, after all you want to the background not to take over the foreground image. But that doesn’t mean that they have to be boring. This image is on the cool side (I somehow think M. C. Escher would have approved of this image).
Another sort of cool thing is that the image was created in Adobe Illustrator, therefore a vector image. So this image could be made in any size. This makes the background very flexible. Another thing about of the image, it was not created with 3D software – this is a 2D image. So for a “boring” background image it is rather remarkable.