I’m willing to accept if this impossible…
So far I’ve tried putting the projection image in front of the light… the method we use in Cycles. This… would work with a line-drawing. I can’t get shades of grey and I certainly can’t get colour.
There’s also the possibility of putting an image texture on the light it’s self… I found this thread, but didn’t really understand it: https://developer.blender.org/D3445
This is something I would like to be able to do, but I understand if it’s not actually possible… or that it may be implemented in the future.