Damn... I hate that picture...

Anyway, I've always thought it represented "emptiness" the one who means the most to him has just been shown dying in time compression (so he thinks) and he is all alone again.

Basically Squall has been alone in his mind, and now that he's finally opened up and embraced thoes around him (albeit awkwardly) he is now alone physically. It's basically time to give up.

Either that or it's a fault in the graphic, but I doubt that.