I went back to my mood board and picked out a couple of photos that appealed to me. I still liked my original mockup with the textured bodice and the “ragged” skirt, but I wanted to try out a few ideas for the shoulders, neckline, and sleeves. Here is my current favorite (which still needs a lot of work):

I am not crazy about the bell sleeves, but they are better than the other things I’ve been considering. I like the sleeves because they suggest wings, but they also draw the eye downwards, whereas (in my opinion) the rest of the outfit is traveling up. The eye lands on the bright yellow/orange skirt, then travels up to the red bodice, giving a feel of fire traveling upwards. Then it hits the sleeves and the direction changes suddenly. Very distracting. Of course, it may play out better on an actual person, because when looking at a person, the eye is drawn immediately to the face, in which case it would be traveling down, not up. But still, I’m not wild about it, though it’s the best of the mockups I’ve made.
Here are some of the other things I tried, and the reasons I don’t think they work:

This doesn’t work because the wings look stiff and pointy, while the rest of the garment flows smoothly and softly. Also, the wings establish a horizontal line up top that is totally at odds with the straight up/down flow of the rest of the garment. It also suggests a triangle, which is what I tried next, with disastrous results:

Here the hard, feathered feel is totally at odds with the soft drape of the skirt – it feels rather like a muscular, butch heroine on top, and a sappy romance heroine on bottom. Yuck!
Then I tried adding long, flowing sleeves, which is how I arrived at the bell sleeves:

The bell sleeves aren’t so bad, but the high neck was a real problem; now it “feels” to me like the wearer is choking.
So I put a V-neck on it, which I liked better and which is my current working mockup (it’s the one at the top of this post). I’m still not satisfied – wondering the bell sleeves would be better if made a little more textured in flavor (there’s a smoothness to the sleeves that is not echoed anywhere else in the piece) and maybe made a little shorter, about waist-length, so it doesn’t compete with the rest of the garment.
Finally, here is the one other effect that I really like, but can’t figure out how to integrate: the loose, flowing overskirt that billows out as the wearer walks. I think it’s totally incompatible with the draped folds, though it might make an interesting cape or something. (I keep thinking of the X-men superheroine Phoenix, though I don’t believe she wears a cape.)
Anyway, I haven’t arrived at a design I really like yet, so time to mull over things (and contemplate my mood board) some more. It’s still in gestation, and I expect to go through a lot of design changes before I’m done.
Have you read The Hunger Games? In one of the series, possibly the first, the author describes a dress of flames. The v-neck version minus the long bell sleeves reminds me of it.
The bell sleeves might be better shorter? They are nice but overwhelm the whole because (I think) the skirt length doesn’t balance them.
scoop neck and cap sleeves? the skirt will be the focus then
Hm. Could you integrate the billowing overskirt into a transparent/translucent outer layer, like this dress from Titanic? Also, “Firebird” ballet costumes.
Have you been looking at any pictures of birds? One thought that occurs to me is that birds have differently textured birds at different parts of their feathers. Hard in one place, soft in another.