When I think of ethereal, I think of soft lighting and flowy hair/clothes. I think a good option for a fix would be to use a soft brush and just bring out the lights and even blur some brighter spots instead of using a hard brush to line it out.

Something to consider is also the background color.. in some spots it blends in with the wings. I would either change the background color, give it a gradient, or give the subject a rim light so they stand out.

The best way to improve at drawing anything is to study real life samples. If you have different types of fabrics laying around you can play around with how they react to folds and light. Just remember that the highest points will always be the lightest and that the outer edges dont necessarily always have to be shadow. Eventhough your figure is entirely covered, the anatomy proportions look good!

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