Short answer: Most certainly only your account information and that you use this application.

Longer answer: libspotify is just a binary library so I don't really know what goes on inside, but since the library was distributed before this statement one can assume it just does what it is supposed to do, and that does not include accessing any information of yours (except the account).
It can however access your disk at a specific location to cache data locally, and store songs for offline usage.

Thoughts on the policy change (not related to CuteSpot):
If you think about it, if you want a custom image in your playlist the android app probably needs access to your pictures, if you want to see if friends in your contacts use spotify as well, you need to access contacts. But then again since you give them access they could theoretically use the information in a different way as well.