I tried my best make the Sky from dark hyrule castle using screenshots form various places, but I still had to fill in the gaps myself the best I could, since I don´t have the actual MC sky BG. from this I then recolored it to make the Twilight Realm Sky.
EDIT: Rayo sent me the actual background which he ripped using an emulator. So here is that background and the edited Twilight Realm.
EDIT 2: I kept messing with the sky and made normal sky too, which fits so well with the mountaintop background from MC. It can also be used for a MC styled Skyloft