Since Ubuntu 14.04, Spotify uses a low resolution icon in the system tray. You can replace the icon manually. But the icon is overwritten whenever Spotify updates. In other words, you have to fix the icon every time Spotify is updated.
This script is a fork of faviouz/fix-spotify-icon and allows you change icons for Ubuntu Ambiance and Radiance themes.
Run this one-liner to automagically install and run the script:
wget http://git.io/vW2fX -O - | shIf you don't trust me you can inspect the source of the installation script and install it yourself ;)
fix-spotify-icon [theme]- ambiance
- radiance
Do not cry! Submit a Pull Request!