First of all I want to say that this is a wonderful art work
The vibrant red of her dress with the mainly black and white background makes a very interesting combination. I like the ashes effect you added around the wings and also the work you did on the lighting behind the wings. This makes it look quite realistic to me. Also you did a very good job on the perspective and blur.
What I think is the best, maybe not the most important, detail in the picture is your use of the birds. It's unusal to make them gray instead of black but with this background I think black birds would not work so nice and also this makes them look to me like they are covered with ashes too. For me details are very important in pictures and I love to discover all the little bits
The only thing I think could be improved is the lower part of the dress. Maybe a little smoothing could help to hide the folding where it lay on the stairs in the stock picture.
All in all very good concept and excelent execution