Vivid images like those you describe happen across a wide swath of ñanas, Eric, so I don't think they can be used as diagnostic criteria for mapping. As you say, they happen when your noting is especially good, which suggests that they may be a function of concentration more than anything else. It's interesting to notice, though, that we often interpret these quicky-visions in a way that is consistent with the current ñana. For example, if I have vivid images during the fear ñana, I'll find them scary; if I have them during the arising and passing phase, I'll find them inspirational, etc.