Snarry can stand the intrusion of a third party (in, say, a threesome), and is one of the few ships that can. Now I am thinking of *which* third intrusion, it would be, that Severus Snape would not say no to. The result is not pretty (b/c it is gorgeous, canonwise): Ginny Weasley. The ideal third person into snarry would be Lily Evans, b/c Harry AND Severus have strong feelings for her, but thinking of Harry and his own mother like that is...not right.
But what I *really* want to see is a picture of Snape and Harry, well into their age, and still together (in that way), as though it were their first time (passion-wise, not awkwardness-wise^^).
And I *love* the image of Severus's jaw dropping in shock - not just anything has that effect. ;)