Katy Perry The One That Got Away

The drawing seems very two dimmensional, there are very few shadings and there are many solid colors. Try adding different tones/shades of color when you apply your medium on to the drawing on appropriate places. Great details but can do better.
The shape of the head is great though.
The shadows need to be a bit thicker and softer.
It needs to have human figures and features.
The detail under the eyelids are a bit too heavy, try to even the eyes by adding more detail above the eyelids and very few under the eyelids.
Anyways, you did an amazing job on the clothing, and great originality.