Assuming appropriate sensor technology exists, you could detect and confiscate all electronics. I don't know how you would distinguish between the limo's electronics and a camera in someone's pocket, though. I doubt you could make a party limo without any electromagnetic fields in the back. I suppose you could scan people before they get in the limo, but that's pretty invasive -- a little too much like airport security. Plus, neither of these techniques would do anything against non-electronic film cameras. I'm sure there are even plastic cameras that would get past a metal detector. Having very low-light conditions inside the limo would probably fix that problem though, since a non-digital camera is not going to have night vision mode. So, assuming it's feasible, try this:
1) Scan everyone for electronics before they get in, and confiscate every electronic camera found.
2) Make sure there is too little light inside the limo for an analog camera to function.