Photo by Rebecca Johnson
At our church we also created blocks like this using sandwhich bags for a "God Sightings" wall one year. You can stuff one bag with paper, then slip that one into another sandwhich bag facing in the opposite direction to make the "brick.". These aren't very sturdy, but could be glued to a cardboard backing for more stability.
One cool feature of this type of wall (not reinforced) is that if you need to have someone break through a wall, you can (and then just put the pieces back for next time).