Among other things that picture contains a very young Patrick Collison, just above the projector.

When was that image taken?

It would be interesting to see a collection of images from each batch to see a lot of the YC founders when they were just getting started in the accelerator.

That was PG talking about Prototype Day at Y Combinator Summer 2009

Haha, same photo I used in my article about applying to YC: https://medium.com/p/b0a75aa7401f :)