Weird pattern seen in photo

Probably just how the computer is rendering the image.

 

For whatever reason I don't see the image. It did not make it all the way to my screen so I'm really guesing. But from what you say it could be a Moire pattern.

What you may have are two sets of grids are similar scales. One set of grid is the pixels in the sensor and the other is fine detail in the subject.
http://en.wikipedia.org/wiki/Moiré_pattern
See the example of the parrot phot on the above page.

 

It's some kind of demosaicing artefact I guess. See http://www.cambridgeincolour.com/tutorials/camera-sensors.htm there's a paragraph on it. You've got maze-like artefacts.

Edit - this is interesting too http://kammagamma.com/how-we-test/demosaicing-and-false-colors-test

 

it's probably how a camera renders lights together, part of the beyer output perhaps