I don't know where else to post about this. There is no contact information for developers?
I've spent the last month, full-time, building a playlist builder for Android... I have your bright green 'log in with Spotify' button. I have a very obvious 'Play on Spotify' button on each preview clip with album art. I have listed that the app is Powered by Spotify in the Google Play store description. I have complied with every Spotify TOS requirement.
My app has been rejected due to intellectual property usage. I've been instructed to remove all third-party images before resubmitting my app or to file an appeal with proof that I have permission to use these images from the API endpoints you so kindly provide for us. I am happy to send the apk for review. I would be happy to discuss it further if by some miracle someone who works at Spotify reads this.
My app promotes Spotify. It doesn't do anything hacky. It consumes your API and follows your TOS. Your support would be very much welcome.