Nice topic, nice pixels. I just think that the anatomy and pose of the mermaid seem a bit, unnatural. She looks like she's the first Next Top Model to get voted out the show. :d
Also, the boobies are of unequal sizes, although that's pretty normal, I think it's nicer if they were the same size.
Oh and when it comes to pixel techniques, it looks like you pwnd them all. I grant you the pixel master certificate.