As seen on the ad for the gameboy advance tribal edition ad it says you could get a winamp skin if you registered the console itself, i dont know if its through a website since the ad doesnt tell us the URL or anything.
I'm kinda interested what it looks since it doesnt show what winamp skin.
I wish there was more interest in lost WinAmp skins like this, there's a lot of interesting ones out there that haven't been archived in the WinAmp skin museum like this one animated Hatsune Miku one that one of my friends was interested in finding, I imagine if they're anywhere they've got to still be on people's old hard drives