Frankly, and I provide the disclaimer that I don't mean to offend anybody, it is obvious from the photo's they were engaged in consensual sexual activity. To argue that Ms. Arias elaborately staged the photos as well as performed acts on herself to mimic that they had a sexual encounter, while possible, is not the optimum conclusion that can be drawn from the evidence we have as of now.
1) Jodi did not want these pictures to be seen and intended that they would never be seen. This does not speak to someone who had staged a fake sexual encounter with someone so as to blackmail someone or tarnish their name in the hopes that these photos would be used.
2) It has already been stated about the other photos, as well as the evidence within the admissible evidence, and the gyn report.
3) Mr. Alexander and Arias had sex before this encounter, even when there relationship was strained, or had taken a turn for the worse.
Whether or not they had sex means very little as to the actual murder itself, the pictures mostly prove her presence at the scene during the actual murder. However, it could provide insight into her psych, her motives for planning this, and how she was able to manipulate Mr. Alexander, a man much more physically stronger than her, into a vulnerable position. It also speaks much about their relationship itself, and why Arias attacked Mr. Alexander with such fury.