I did a 6x6 rasterbated version of this image:
I bought 9 A3 black mount boards and on each of these i put 4 of the A4 pages and put up the A3s spaced apart to give thick black borders around the A3s with the thinner white borders between the A4s.

You can see part of it in the image i posted here but the photo quality is horrible and doesn't do it justice. I will see if I can get a decent pic for you later.

http://www.flopturnriver.com/phpBB2/...585&highlight=

If you are going to rasterize the image (closeup: http://www.gribnick.spb.ru/images/bl...r-closeup2.jpg you can specify the pixel width in the rasterbator application)
you shouldn't use an image with fine detail as this will get lost. If you want to use an image like the one you posted you are better off just using tiled printing (just set the pixel width as small as possible) but I think this will just end up looking like a cheap version of a big poster whereas rasterizing the image (preferably black & white) gives it a really nice effect.