I don’t think it’s the cops since the pictures are used to piss off the Jocks. Originally I thought it was Quinn, as a candy cane appears on the floor between MCs first visit and the point where the picture is revealed. However it never made much sense that Quinn would do that to the Jocks.
That leaves 2 possibilities. The nerds in some form of revenge with Sally as their agent, or and this is what I’m now leaning to, Vinny.
Vinny would make sense if he is trying to fuck with Quinn. If he can make her look like she isn’t performing then he might be able to get the college back as his area. (Logic being Vinny plants camera knowing DIKs fuck in there, find’s a useful picture and sends it to Dawes, along with ChadxTroy evidence to the Alpha’s, the Alpha’s react and get more attention them and can’t buy drugs, Quinn’s business suffers)