Ok, a really small snake body. If you use a tyranid you could also make som nice extra claws for your model.
If you dont like feather wings, try the dark-elf dark-pegasus wings.
Since you want a snake body to the rather small deamonette you might try for a split tail (two smaller ones extending from the legs/hips maybe, then intertwining below?). I think there are some split dragon tails, if you feel like spending