Not sure, but this is an idea... See if you can add edges to the scribbles. What I'm trying to say is imagine that you are drawing on the walls, not the photo.

So if I take the halo as an example, it looks flat at the moment, but if you add some shadows and gradients, you may be able to make it look like you've walked into that room and drawn the halo on those two walls.

Just an idea.