OK, I have just finished my own favorite classic WinAMP skin. It is based on the old Spinner24bit skin (which for some reason is not available via winamp anymore). You can even see some spinner left-overs next to the main Pause, Play and Fast-Forward buttons.
I have removed what I didn’t like about the spinner skin, changed a couple of details and made the few colors it had a little warmer. It is mostly dark grey, and I really like it, because it has no bullshit in it and is very easy on the eyes.
You can download/install the skin from here.