Its clearly a penis. What else could it be in the context of the man standing there? Why else did they replace him? It is an anatomically correct huge penis.
Of course it is. Good for you for recognizing the image. That means that the message is no longer subliminal for you. Subliminal refers to 'below the consciousness'.
For those who cannot 'see' the image, it is still working subliminally on your brain.
For the science behind brain function and subliminal images:
http://www.jneurosci.org/content/18/12/4697.full.pdf+html
Neural Response during Preference and Memory Judgments for Subliminally Presented Stimuli: A Functional Neuroimaging Study Rebecca Elliott and Raymond J. Dolan.
A region of right hippocampal gyrus was activated in association with objective stimulus novelty in the absence of awareness of novelty.
(italics mine)
More scholarly articles and studies concerning subliminal stimuli: