Not much at all, you can basically vary between two wing poses on each side with the setup GW gave it. Though the second option that's not on the box is nicer, more parallel with the ground and stuck outwards a bit more.
That sounds like what i'm looking for. The box pose is totally incorrect for a creature that is upright, for a hugging-the-ground creature like the Terrorgheist whose wings also function as arms it is just right, but the Stardrake has four legs and the wings are just wings. There is no reason they should be pointing down that way.
Liking the Stormcast as well, looking forward to seeing how they fare in your local campaign. For Azyrheim!