It's not the final photograph in the series, at least per the original flickr album is concerned. It's just the only one of them all where; a. Summer isn't smiling, b. the accompanying human isn't "of the Wolf Shirt vernacular," so to speak.
That gif is full of win.
The series of photos is awesome, hilarious, but also really quite sad. Sad in a "I feel bad for mocking these people's priorities and taste." Because the images reflect a piece of the population that enjoys much of the same interests I hold. The humor comes from the bucket of awkwardness and apoplectic expressions.
Maybe if I was snuggling up to Summer Glau in front of that Jostens background for a glamor shot, I too would look like I had just undergone the belt tuck routine. But I would be wearing my wolf shirt ironically.