Spinner can be reskinned according to your own style requirements using a Nine Patch.
As an example, see this Nine Patch:
As you can see, it has 3 extremely small areas of stretching marked.
The top border has only left of the icon marked. That indicates that I want the left side (complete transparency) of the drawable to fill the
Spinner view until the icon is reached.
The left border has marked transparent segments at the top and bottom of the icon marked. That indicates that both the top and the bottom will expand to the size of the
Spinner view. This will leave the icon itself centered vertically.
Using the image without Nine Patch metadata:
Using the image with Nine Patch metadata: