http://homokaasu.org/rasterbator/

Use that to print the image (the higher the resolution of the original, the better), then I used 3M spray adhesive to secure the sheets to foam boards (from www.foamboardsource.com), then I attached to the wall w/ velcro so they would "pop" off the wall a little.

I made a thread on this a while back; all the pics are gone now, though: https://themustangsource.com/showthread.php?t=450085

http://forums.bradbarnett.net/showthread.php?t=450085

The picture links I used are dead but I think you'll get the general idea. Send me another PM if you have any specific questions after reading that!