From reading Win's stuff, I got a different impression than Andy030. I interpreted Win as saying it's OK to "augment" the Image Stream with imagined things. For instance, as you see something playing out, imagine what you might hear or smell and add that detail. Somewhere (I think in his tape set AND The Einstein Factor), Win suggests this as a technique for getting the Image Stream going. As you develop comfort with the process and you get more in tune with your own internal experience, you'll have less need to augment.
My own experience supported Win's suggestions. As I "added to" the Image Stream experience, I got more wrapped up in it. Eventually, it was no longer an issue because the experience grew vivid enough that the experience seemed complete.
