Allow anyone to press a function key to screenshot the area you are currently in, it is then saved to a file with the region coordinates. Do this a bunch, and you can then stitch together a large image like the World Atlas series of blog posts.
I don't know a way to make the world atlas thingy but you can always use the megamap at http://8bitmmo.net/megamap/ :P
I know a way to take screenshots. Press the Print Screen button and then go into a system like windows paint, then press Ctrl + v. Simple as that! :D