This is a little off topic, but:
For a simple video wall, where you use separate PCs going to various monitors, there is a great free program called input director. It is an IP-based Keyboard/Mouse Switch. Just like you used to have a physical KVM, here you already have your Monitors. This allows you, once configured to get rid of all of the keyboards and mice laying on the desktop, and use 1 set to control multiple PCs. This can be very impressive for people who have been used to the clutter. Great for control rooms, demos, trade shows, etc.
The software supports PCs with multiple monitor outputs and you can configure how they are arranged, and neat options like wrap around and shared clipboard.
Input Director - Software KVM to Control Multiple Computers
List of features:
Input Director - Software KVM to Control Multiple Computers#features