Praise be to Allah
There is no reason not to put the screens in the front of the mosque, so that by means of them the members of the congregation can see the imam, if there is a need to do that, such as in the women’s prayer space, and upper and lower floors, on condition that these screens be used to transmit the image only, and are not used as televisions per se.
In fact this is something that will help people to follow the imam properly, by seeing his actions and movements, and it will reduce the confusion problems that result from not knowing what the imam is doing, especially in cases where the imam makes a mistake, or he does the prostration of recitation or the prostration of forgetfulness.
But the worshipper who is praying behind him should be looking at the place of his prostration, and not at the screen, except when there is a need to do so.
The fact that there are no such screens in the mosques of the Haramayn does not prove that they are not allowed; each mosque has its own circumstances that are appropriate to it.
If the screen is used to display useful Islamic information, then it should be behind the worshippers and not in front of them, so that it will not distract them whilst they are praying.
If what is meant by the question is using these screens during the Jumu‘ah khutbah, for example, there is nothing wrong with that, because if the members of the congregation look at the khateeb, whether in a real sense or via the screen, this is something that will increase their attention and ability to benefit from the khutbah. Hence the Sunnah is for the members of the congregation to look at the khateeb.
And Allah knows best.