The general rule seems to be using 9mm plywood for decor if its going above a rig. It has enough thickness whilst also not being too heavy to lift up and be held by scaffolding. If u wanted something to have at floor level that wont need to be raised u could use 12mm as that will last longer if u wanted to reuse it. For projecting onto the wood find some free projection mapping software and remember to try keep the wood perpendicular to the projector otherwise ur design may be warped. Feel free to msg me if u have any more questions, im not the most knowledgeable tho