What I say will not be constructed and most or everythings of it will be wrong.
For the photo of Arieth fucking others, 2 were taken on a phone but we don't know which phone, if it was on a DIK phone it would have been on the DIK computer or only the Rusty one since Jamie lost his phone. Also the last one was taken by a camera ? It would mean it has to be someone who has easy access to the camera or that the camera send what it take already on a computer. If the first photo was on the DIK computer it would mean that someone had access to Rusty folder. The only who could have an access to Rusty's folder would be Tommy and Nick since they know him from the start. To not just say it's a DIK, the others characters that I can think about are Quinn, Heather and Elena. The things is, who would need to have the relationship beetween DIK and Alphas worsened . The only ones that we are sure would be Quinn and Tommy, and while both would do it, they would not hide that Chad is gay.
Now is it the same person for the photo and the Cathy cluck ? Probably. I said many months ago that there was perhaps a theory that the DIK mansion was trashed by 2 differents groups, the Alphas at first with the Dildo and the other group who did the main trashing. If all these 3 things were done by a single person, the only character that I can chose would be Vinny.
What would be his reason ? The reason would be to make the drug ring of Quinn fall by making it public, because the Alphas and the DIK are her main buyers. He could want to be the sole seller. Perhaps he had the help of Nick, but he would be one of the character who could access Rusty folder (unless we can't access the folder because DPC said NO!).
For Riona's real stalker, it can be any reason, but there is the possibility that Riona was right, that she is targeted because of the drugs.