It would be cool to have a music visualizer that syncs with music that's built into Spotify. It would be great for vibing out by your computer while you listen to Spotify.
This is already possible on the desktop client, although it's a bit hidden.
Just type in the top left search bar spotify:app:visualizer and a visualizer app should appear for you. 😉
For possible improvements to the current visualizer, please add your comments and kudos to this thread here: https://community.spotify.com/t5/Spotify-Ideas/Update-Visualizer-Desktop/idi-p/1008697