MI, I see you've done your homework
"Pictures" is perhaps an unfortunate word to have been used by Hubbard; but I don't know what other word might have been chosen at the time.
In actuality, what we are dealing with on this subject is "spiritual impressions," or put another way "impressions recorded in/on you spiritually."
The phenomena is that we as spiritual Beings have been involved in events, impacts, et al that have left an impression in/on us. That's one way to express the phenomenon. The other way to express it would be to say that as a result of our contact with events/impacts our spiritual condition (as extant at any point in time) got altered, and that alteration "lives" on until reversed or "erased."
The "three dimensional" aspect of some pictures referred to above would be better stated in the terms that the recorded image/impression of past events is three dimensional and holographic. When they go live one can find oneself
in the thing and it can be as real as the PT physical universe . . . but not necessarily as "solid." The image can appear to be throughout you as a Being and you throughout it. And you can experience, perceive, see smell etc all of its content. One incident image/picture I encountered (the description of which is on ESMB) had me experiencing the motion of the sails of the men-'o-wars of the early 19th century event.
The confusion that arises in this subject is due to the fact that lots of folks do not get their past events 3DH. They only get them as flat 2D "pictures." Some folks have so avoided, altered, denied, suppressed and/or otherwise occluded these records of their past existence that they say there is "nothing there," and/or otherwise say all this is bullshit. Some folks have solved the "unconfrontablity" of the issue with the solution of avoidance of such an extent that they are totally absent from their past unwanted experiences, and so they too will assert it's all bullshit and that there is nothing there.
So, to answer the question in other terms, one could say: some folks are aware of the records of their past existence and experiences, and others are not.
As to the "mind?" Well that is a construct we spiritual Being have created to handle, control and store all this junk we did not and do not want to now experience.
Recovering one's willingness and ability to experience and know "anything" and to be responsible for and in control of such, is what has you free from being effect of it and overwhelmed by it. That state is attainable.
Rog