[Kevin Sio] “I went to an off white more like pale pale grey seamless paper.”
This may not be true anymore, but I remember reading that at the end of the chain, the consumer tv set acts like an exposure meter searching for an 18% gray card. That is, it will darken a white image, and lighten a dark one.
Whether that is true or not, I agree with Kevin that you should use a shade of gray. It will seem white enough anyway. In Photoshop, you can use the eyedropper tool to match the background of your graphics with the “gray-white” background you shot live.
The other approach is to use a deliberately mottled background with some pure-white in it and dissolve to your graphics as per your original plan. It isn’t the original concept but would be easier to pull off and might actually look better; the pure-white areas of your background would appear to “bloom” into the pure-white graphics.