I find this story idea really interesting - the fact that they are acknowledging Snape's...(not sure what to call it), "thing" he has for Harry's mom... Or was he only innocently looking up there and Harry is just teasing him? But no, he blushed, so it must mean...anyway my first interpretation was that that's exactly what they were doing - acknowledging it, but then I was second guessing myself (is that really what the artist meant?).
I love Snape's face in the panel where he is looking up at the statue and his face when he says 'insufferable whelp'. Also in that panel (the insufferable whelp one) I love Snape's arm over Harry's, and the fact that they look like their bodies will fit so well and so cozily together. :-) And the last panel is wonderful with them invisible, only the footsteps in the snow. That swirl of snowflakes gives it this just magical feeling.
I do have a question though, are they sneaking? Because Harry is with Ginny? 'Cause I won't like that. :-) Why need for secrecy?
I also liked the statue and even the idea alone to have the statue and have a story around it. And of course, their initials on it, awww.