I (author of Webamp) worked with the internet archive to archive ~50k Winamp skins. The collection even features Webamp integration is you can try them out in the browser. https://archive.org/details/winampskins
I always preferred Geiss, but either way, I wish such visualisation capabilities were built in to Spotify... Or is there a suitable in_xxx plugin for Winamp that will let me use its visualisations with Spotify?
I'm using a Macross Plus Winamp skin for QMMP as I write this, so it was funny to read your comment...I got so sick of iTunes that a few years ago I went back to the old way. I wrote some scripts to select & generate playlists and bound the scripts to keyboard shortcuts like Ctrl+Super+Media Keys. QMMP has been really solid.