This is beautiful. I love pictures like this. Pictures that express nothing raunchy or sex related, just genuine love.
The thing that strikes me is how innocent this is, yet the intense love it still there. The way Rarity is holding Spike is a way that expresses true love and devotion, while the way Spike looks up at Rarity suggests deep affection. It could be looked at as they're lovers, or even a more maternal love. Either way, I support this shipping one hundred and twenty percent.
I'm surprised people keep saying nay to this. Rarity is clueless and probably not girlfriend material for Spike but she does care about him and isn't fat from delivering him affection when he needs it. So I dunno.