Not only was she the goddess of the starry sky, married to her counterpart, Geb, the god of the earth - she also was the mother of the gods - Isis, Osiris, Set and Nephthys. (Some myths ascribe her a 5th child.) She was the boundary between the ordered universe and the chaos beyond, the protector of the dead and their souls, and the form which Ra followed through the sky each day and night.
Nuit was associated with the maqet, a ladder by which Osiris and other deceased souls were able to climb into the starry expanse, so I choose to design her headdress to have two long extensions down her back to symbolize a ladder. Also, she was often represented with a pot on her head, and I have echoed that with the round vessel shape around her head, containing the dark expanse, containing a thousand souls, containing the power to create gods and goddesses.