What are you actually trying to do? Do you want to display the same content on multiple displays? Display different content on each display? Spread a single
image across multiple displays? All of the above? And how many displays may be involved?
Are you expecting people to be able to see what is displayed or is the goal to have color, motion,
etc. without the actual content being critical? The latter seems likely since you posted this in the Special Effects rather than Multimedia forums, however if being able to discern the content is desired then unless you are working in a rather small space or use a multiple display video wall type approach, the potential viewing distance for content on a single
flat panel type display is likely to be limited.
What is the content and the source for it (PC, DVD, clip server,
etc.)? What video connectivity and signals do the source and displays support?
What potentially related equipment do you already have or have available to you? What is your budget?
People can only respond based on the information provided so the more information one provides on their situation and what they are trying to accomplish, the more anyone can respond to offer solutions that fit their needs and avoid going down
dead end paths.