There are a few sticklers about a GPS receiver photo but they are very few. I wouldn't worry about it and would post all of my visits without it. If someone deletes the visit forget about it and make a mental note that visiting that individuals waymarks may not be worth your time.
I usually have the GPS photo because I use a photo to record the lat & long but if I don't have the photo I don't sweat it and if others do not have one I don't worry about that either. GPS photo shots are relics from the old locationless cache photos where they made a little more sense as proof for the find. Here they don't prove anything other than a photo of a GPS unit is just a really ugly photo. A picture of my GPS unit with me included as some try to require is an even uglier one.