Does the first one mean you've never had *your* picture taken when you were naked or never taken a picture of someone else who was naked or never taken a picture of someone else while you, the photographer, were naked?

It is a pretty ambiguously worded question. Though I think in terms of pure grammar it's actually asking the third interpretation. I was thinking more along the lines of your first interpretation when answering, though in my case the answer would be 'no' for all three options.