This is a father beautiful little piece of pixel, I like the colours most of all, they are rather soft and nicely done. The first thing I would suggest is more shading, there only seems to be minimal shading and this is most obvious on the face and body, although she shading on the tails looks very nice. There should be shading under the jewel and the legs should cast shadows. The highlight on the head looks like, but it doesn't look right against the shading.
The animation is nice and subtle, and very smooth, but I would recommend adding a little more animation, for example, on the tails. Simply moving something up and down requires little effort, actual animation in the picture may look more effective and worthwhile.
Finally, while I like that you haven't used black for outlining, the brown seems to stand out a bit. Try using a colder blue colour, just a few shades lighter than the colour next to it, for a more effective look. It seems that one the shaded parts you've used a lighter colour for the outline, which makes it look a bit 'blurry'.
But over all, very nice work, and an adorable piece of pixel art!

Also, I wouldn't recommend trying to sell this. The point selling function is designed for selling actual resources, such as brushes. If you intended for this to be used as a resource on a website, you'd have to put a watermark or signature over it to stop people simply stealing it. This seems more like a work of art that you want to show off than something you want to sell.