STALKER Shadow Of Chernobyl Easter Egg - Hidden picture of the developers

In the level Dark Valley, there is a lab you'll have to enter to continue with the main story - Lab X18. At the very bottom of the complex you will encounter a Pseudo Giant, a creature of around 3 meters height, with large legs and small arms. After you've killed the monster, turn to the right wall of the large hall. You'll see some stairs and a catwalk. Get up there and turn to the left, there's an opening in the wall that leads to a room with green tiles, a fridge and a blue chest. Above this chest on the wall there's a picture of the developer team of STALKER.