I wouldn't call it a picture line, but I don't think that really matters. The figures used in closed syllabus work are supposed to come from the syllabi of member organizations (so, figures from the DVIDA syllabus, FADS, Arthur Murray, ISTD, etc.). A throwaway is probably the quintessential picture line in ballroom but it's not in any closed silver syllabus that I know of, so my understanding is that it would not be allowed, even with the #3 you quoted above. But again, I'm not 100% sure and I have not yet found a consensus among even adjudicators or invigilators regarding what's allowed.
I've long been an advocate of more clear guidelines for closed syllabus work in american smooth, and this is just one more example why...