That is a well done dress. Only fix i'd have is another layer between the hoop skirt and the dress so the hoop isn't as visible, but I digress. As for the photo, the lighting is perfect. The fact that the actual light stops before her so she doesn't have the odd spots on her is wonderful. Even though she's in the shade, the red still stands out nicely. The angle is nice too. Though a bit of light on of the face so she's not in the dark might be good. Though it might affect how the rest of it looks too. I ramble.
There's always room for improvement, but by comparison to the vast majority of cosplay I come across this was very well done. I was quite impressed.
As for the light on her face it was something I was worried about. All through the day the hat went out of it's way to make me cry about the lighting. Think of it like a beautiful, feathered photographer slayer. >.< In practice I could probably dodge it brighter using the GIMP, but sticking to my "au naturale" approach to things I decided to post it - sans any modification beyond some global exposure compensation - as it was.