Trying to build out a room with 24 TV screens all around the room controlled by one computer. Each screen would have to be able to display different content/images. No video/gaming displayed. Just high quality static images. (preferably HD quality-Yes I know my source images would have to be high quality, just want to make sure the technology can support it) Need the ability to change the static images on the fly utilizing wifi/tablets. Any suggestions on what kind of rig to setup? HDMI/DVI/DisplayPort? What kind of video cards should I be looking for? Cheapest solution possible please.
As far as controlling them individually with tablets or wifi. Not sure what you are looking to do here, but it will not be cheap. You are looking for something probably proprietary or special use. Most likely you would have to seek the guidance of a sound and media company that could put together a custom package. My guess it would be tens of thousands of dollars or hundreds to really do that right.
You would have to see if Windows could even run that many displays and the desktop resolution would even be supported in windows. As mentioned it is probably a specialty build with a non windows OS. But who knows. This is not a hobbies questions it is a corporate or large entertainment realm.
There are a number of workstation motherboards out there that also support (4) PCI-E x16 cards. I do not believe you need it to support Crossfire because you are using them independently. But the Asrock should work, in theory.
Distance of an HDMI cable will matter at some point and you could see some signal loss. However, I think 50' would work. Most cables that length at pretty thick and are $50. You might find you are going to spend a lot on HDMI cables.
By the time you pay for fire pro cards and HDMI cables alone it would probably be cheaper to slap a thin client on the back of each monitor. Really all you need is a device that can send a video signal and be network controlled.
It wouldn't even have to be network controlled I suppose. Something cheap like a rocku, or anything that can do full screen Web browsing, or a TV that can. Point them each to their own webpage being served on your local network, when you want to change content log on to remote desktop or webserver and just change the image that monitors Web page is showing.