Tips from "Been There"
About six months after you paint a white screen on your wall, you will wish you had painted it 12" to the left (or right or down or up or bigger)
If you paint a mural around your white screen, you will have to wait for the artist to pass away or leave the church before you can repaint where you 'should have' put the screen. Corollary: If you hang a screen over the mural, the artist will pass away or leave the church. 
About 2 years after painting the screen, you will decide to move your Video workshop to a new room, or you will decide to reorient the seating in the room.
My advice:
If you don't have a nice flat wall to show your video on, do one of the following:
1. Mount a curtain rod and have a thick white cloth rolled on it that can act as a screen when lowered.
Or 2. Get a wide white vinyl blind from Home Depot and hang it.
Be careful about designing the room with murals around a white screen area. You don't want to have an artist put their heart and soul into a mural that you may have to cover up at some point, or obscure when you move furniture or cabinets around. Corollary: Jesus doesn't like to be obscured by your movable closet.
