So the first thing I see is the head seems a bit small in the back. This is a classic mistake that lots of people make but its no big deal and it takes a quick fix adding a bit more volume to the back of the head.
An argument could be made that the distortion from the camera lens could cause this as her face is pushed so far forward.
The next thing that I would recommend is to keep the rhythm of the snakes as a rhythm theme among the entire piece to bring some cohesive feeling to the portrait. Keep this style of rhythm all the way down to the small elements including the snakes tongues. The tongues have a sharper shape design to them that seems out of place because its not similar to the majority of the piece.
Last I would add more snakes to push the pose some more. Fix the ear anatomy. Correct the lighting on the hair and snakes to match the face lighting. Lose the orange line art as a necklace because it seems slapped on and more of an afterthought. But could finish it out more as an analogous color. It sticks out to much as an orange and pulls away from the focus of your piece, the face. It may have added a bit more of balance while you sketched it out but I think its fine without it.
I hope that helps and good luck with your t-shirt.