If that looks suspiciously like the iconic photograph Raising the Flag on Iwo Jima, except in Halo, that's because it is:
Sometimes words simply can’t do an image justice, and that is the case with Band O Brothers. Modeled after the historic photograph Raising the Flag on Iwo Jima, the Halo screenshot version is near flawless, wonderfully patriotic, and has an emotion-invoking impact immediately upon viewing.
From the Top 10 Best Halo 3 Screenshots of All Time at Hawty McBloggy: http://hawtymcbloggy.com/2010/07/06/top-10-best-halo-3-screenshots-of-all-time/ - via Wonderland
Fake posed propaganda, just like the original photo.