In response to The Hangover II's completely tone-less, tasteless, and inappropriate use of iconic imagery, I searched the internet for a review which also mentioned this mis-fire. Here's my comment based on Roeper's review of the film:
Thank God one reviewer has said it! My husband, brother and I thought we were the only ones to notice the horribly offensive and far, far from funny re-enactment of the iconic Viet Nam war photograph of a man being executed by a gunshot to the head during the end credits. While I argued that there is no way Phillips could actually have thought this would be funny and had done it unintentionally (using an image stuck in his head but not purposefully referring to this horrible image), my brother and husband argue that he intentionally used it and thought it would be funny. Regardless, I am happy to hear someone else point out its taste-less-ness and as an end to what had in general been expected and tolerable offensiveness, closing with this intolerable image has left us with a terrible taste in our mouths.