The faces must be at least the size of a small building, like the ones depicted in this image.

They must appear at some time before the closure date of this market and be more than just still images of faces - they should be able to change their expression and interact in some way with human passers-by. The nature of this interaction can be broad: it can be anything from passive observation (like continually staring or watching someone), to friendly chatting, to something more mean-spirited like spitting on people.