Irrespective of who the first model was and who the second model was, when the first pics came out oh so many years ago, they set a standard and attained a level of success in the artistic world for very specific reasons.
Just because someone (even if it is the same artist), clones the style and idea and changes the focus of who is painted will not make it another success. If Davinci painted the Mona Lisa, and it instantly became the success it is today, back then... and then he painted another identical version but this time it was the face of someone less attractive, he would be devaluing his first work as well as the second work... and possibly all his works in a way by tarnising his image to some extent.
The pictures are purposely placed one after another, it is meant as a direct comparison, becuase it is a blatant retry of a pictorial poses, positions and props with another woman.
There are woman WAY better suited to be photographically captured other than Lohan for this goal, whom my opinion, displays a standard of womanhood that is as low in appeal as Monroe's pictures brought to new heights.
Photographically, its a type of recreation. I think we can all agree to that. If I was a famous photographer, why would I need to recreate a set of shots that I had previously taken and had great success with, again with a subject that lacks the physical and sensual qualities of the first subject? Why demean the value of my first work?