The wings annoy me for some reason, but other then that VERY good work!

* the volumetrics of the dress are very good.
* of course more of the original expression (and more facial definition) can be expressed even in these few pixels.
* if you tweak the greys to be more blue, you should be able to reuse them as highlights on the wings -- which will make them look less plasticy. turning the dark green into dark blue should also help.
* the wing highlights look plasticy because they're so rounded. the link you gave (and others in whtdragon's gallery) suggests that they are not rounded like that. More like a bat's ear (the membranes stand out somewhat and block some light, so a mild spiderwebbing effect is apparent depending on the light angle). the short is, you have much of the highlights convex on both sides but they would probably be better concave on one side.

That's a pretty nice sprite there mate, very cute.
Great job