This is a rather disturbing image. Having said that, it is a well done piece of digital painting. Great blending and tone variation on the skin.
Once you get pass the "Zombie love" aspect of the image, you can appreciate the broader theme, which I see as the parallel between carnal embrace and carnivorous consumption. Mixed with this notion is the sense of a persisting humanity and desire for the intimate embrace, even if we are mindless flesh eating creatures. Of course sexual acts are the most primal acts we engage in; no advance human intelligence required.
I'm not sure what is suppose to be happening with the left figure's mouth here. It looks as though the area around it is cracking rather than being devoured by the other figure.