Since the theme is "working together is better than working alone", a group of octocats holdings hands/tentacles together would be nice. The octocats should be varied sort of like the ones here: http://octodex.github.com/ (maybe to a lesser degree, but the effect will be diminished if they all look the same).

I find the trend of seeing every change Github or Bootstrap makes on the front page of HN even more disturbing.

look at the footer