To see the hidden party happy snap picture, first you need to download the Starcraft 2 Cinematic Trailer from Blizzard, because it has the highest resolution. Once you have it, open it up within an .avi player or video editing software. If you are using Windows Media Player, start it playing then click stop/pause. Now click in the seek bar to get to the 00:02 mark, (around the end of the 00:02 second mark). It's within the trailer just before the second flash of static in the logo opening sequence. If you are lucky you will get an image of a happy snap at a party, if not you will have to keep clicking around the 00:02 mark till you do.

If you are using video editing software, zoom all the way on the frames, then go the frame at the 00:00:02:07 mark and you will see the picture. The picture itself is placed in the background of the static flash, once you find it you will see everyone in the frame cheering with drinks in their hands, and a large shirtless guy.