A neat solution to create a videowall made of discrete displays that can play a video or a presentation movie.
It requires one Pi for each display with one additional master controller Pi. The input is by USB.

Roll your own installation instructions are here

The PiWall software package makes it possible to build video walls of arbitrary size by combining a collection of screens, adding one Pi per screen to drive the relevant portion of the wall, and a master Pi to rule them all. We have been busy packaging and documenting a free version of the code and have now made this available on the website along with instructions about how to build your own PiWall.

via PiWall – An innovative video wall system .