I'll chime in here. I personally have posted adds on Canuk Audio Mart(Canadian Site) with generic photos that I have just grabbed off the internet, in fact I have a couple of cartridges listed right now that I have done this way. Sometimes I find it a little easier this way, as I tend to take poor pictures, but I will provide actual photos if requested by the potential buyer. I did not think that this would be a big deal to the interested parties. I actually sold an Oracle Delphi turntable a year or two ago with a pic that I just found on Google images, and got a response a few days latter from the actual owner that the picture was from. He was not upset, in fact he found it quite amusing. We spoke and I explained to him my practice of doing this, and he was fine with it.
After seeing this post,perhaps I should reconsider this practice.