As a new image starts to develop start describing it as it unfolds. Even when talking to a tape recorder I find it helps if I think of someone as listening for me. So when a new image starts forming I start telling them about it.
When images show up again in the image stream describe it in other ways. if you focused on colour maybe you still need to cover how angular or curved it is, it's size and vibrance may have changed look for stubtle clues like that too.
If you have similiar images showing up from image stream to image stream that cool. Your mind is starting to help you uncover the code. It won't be that unusual for image streams to almost be the same on many occasions, especially if you're asking the same question over and over. You'll give yourself a more creative license when you are okay with the images being similar and then give yourself permission to make it up.
One of the most effective ways I learned to visualise was to stand infront of a painting look at it for 20 to 30 seconds and then close my eyes to see what I could "remember" or see with my minds eye, opened my eyes for 10 seconds and do it again. The whole exercise took about 10 minutes but it helped me to change my belief that I couldn't see images in my minds eye. I learned *how* I see them in my minds eye.
If you're somewhere where speaking out loud is a problem then you might get creative and pretend you're telling someone a book chapter, or scene from a game over the phone. There are some neat phones that have recorders.
However only doing it in your mind does not have the benefir nor does it give you anything solid for decoding. Win Wenger has not found anyone having success with it and I personally find that the mind wanders off to easily.
You could try an alternative Image Stream by writing... that is write the image stream and for decoding/debriefing close your eyes and review, it helps if you can talk it then but you may be able to do that when it's more convienient to do so. Somewhere along the line you will want to talk it out loud.
Alex