Garry made a new awesome feature for Garry's Mod 13.
http://garry.tv/post/18269265008/poster-screenshotsBasically if you type this in console:
poster 10
you get a larger image but in fragments.
Then you can stitch the image and reduce the size so you can "super-antialias/smooth" the image.
As for your picture, the posing looks great, but the soldier on the right of the MG sticks out.