I actually have a similar project but I’m going to use a gauze to project on, pref black or grey.
Basically you can project on black, but you need more lumens to get an image!
At least double what you would normally use…
I have heard about using mica powder to add more reflectivity but still keep the screen black, you could try that, and of course use high contrast images!
I’ve done a couple of project’s were projection on a dark surface. On both occasions the surface was painted and textured with some form of reflective material. Here a pic of a gig where the surface is pretty dark but given the luxury of powerful projectors cut through. http://blog.andy-coates.com/?p=571
We also use scrollers with masks on to kill the projector grey to get a proper black.
I just finished on a show called 2071 currently at the royal court London.
We were using Gerriets Show laser Screen, which is meant of rear projection but we used it as front projection with the matt side facing the audience, it worked really well. We had 3 x panasonic DS100XE 10k projections.