Full Screen Music for Spotify is a nice app for Spotify users. As the name suggests, it has something to do with full screen playback.
When you are playing a song on Spotify, Full Screen Music will take the full screen and display the name of the song that is playing, the artist, and when available, some album art. It will also give you control of the music by providing three playback controls: previous, play/pause and next. This is all you need to control Spotify when you already have a playlist set and it is playing. There are different modes for Full Screen Music. The default one shows album art expanded to fill the screen on the back, with the controls on top of that. Then there is another mode that uses a nice grey background and it uses the album art to display the name of the artist. When I was testing this app, I was listening to Eric Claypton, and in this mode, there was a big word in the middle of the screen that read "Eric". The background of the image was the image I was shown in full screen in the previous mode.
Full Screen Music for Spotify obviously requires Spotify to be installed and running. If it is not, you will get an error message and the app will quit.
In short, if you use your computer to listen to Spotify and want to watch images or album art while you are listening to your favorite songs, I guess Full Screen Music for Spotify can be useful.