![](http://farm3.static.flickr.com/2086/2319334950_3d5dc8b3f4_m.jpg)
![](http://farm4.static.flickr.com/3216/2319334090_d0ded05f1f_m.jpg)
You can see many more of them here.
Using the API, I can automatically download a random selection of Squared Circle images, which people have kindly licensed under Creative Commons. I then slice out the biggest circle possible out of these using some functions I've written in Python, with the Python Imaging Library and NumPy. I then paste these slices together in a pile. The API also allows me to properly credit the people whose images have been used. You can see this by clicking on one of the images above.
I have been automagically generating many hundreds of these, and selecting ones I like. It's quite satisfying.