That's a bizarre formulation.
You're saying the conspirators had legit photos of Oswald, taken by Marina, holding a rifle in that backyard, and for some reason (too much time on their hands and an unlimited budget, perhaps?) they destroyed the legit ones and went to all the trouble to substitute fake ones?
Do you even begin to think about the implications of some of your conjectures?
It appears not.
Of course, the other interpretation - that Marina, 20 or more years after the event - introduced this change in her story simply because she simply mis-remembered where she was standing at the time and this means the photos in evidence have always been the ones she took (and that Oswald signed the back of one), isn't to your liking, because it implicates Oswald as owning the rifle and being a leftist.
So of course you will seize upon any other interpretation, no matter how bizarre.
That is not the correct way to solve a crime.
Hank