Depending on your exact requirements, there are several ways to create a video wall (a series of screens set up in a matrix configuration).
Some people might not be aware of this but most commercial grade screens already have this video wall function built in.
For example, the Mitsubishi screens have an RGB input and output port. See the below image:

In order to set up a 3x3 video wall with the Mitsubishi screens, all you would need to do is "daisy chain" all the screen in the following video arrangement:
1. Connect the video RGB output port of Screen 1 to the RGB input of Screen 2
2. Connect the video RGB output port of Screen 2 to the RGB input of Screen 3
3. Connect the video RGB output port of Screen 3 to the RGB input of Screen 4
and so forth.
Alternatively, there are several other ways of achieving the same result. There are devices out in the market which perform the same function. Below is a short list:
1. Stretcher - this device stretches your monitor among four DVI or VGA screens without the use of software


For information about this product, visit our
online shop.
2. Xpander - Expand Your Desktop up to 32 VGA Screens with Video Overlay Support

For information about this product, visit our
online shop.
Feel free to discuss this further.