Don't have pictures, but 3.14 is annotated as a time in the video for 'Turn' and the clock on the wall in the supermarket during the 'Closer' video is at 3.14...
I also remember hearing that the green circle in the video for 'More Than Us' was something to do with it, and that's why the calendar is on '31' at the start of that video and changes to '4' at the end.
Also, 'Side' is about circles only having one side - so surely that's to do with it too...