No worries, pottedplant! Always nice to see new members.
As for the picture you're talking about, I wish I could see or remember the one you're talking about. Either way, I doubt Jimmy was passed out on stage. Probably just one of his stage antics. =/
But then again, maybe the other more seasoned Zep Heads here can answer that one for you.
And YES! That picture of Robert naked is real!
We all thank the good Lord for making that moment in time possible for us fans to enjoy for many years to come.
[Oh, and I can't remember who took the picture, but it was in one of these published books about the band...name escapes me now, but apparently, we can all thank Bonzo for yanking down Robert's swimming trunks when he was coming out of the pool. ]