I "reconstructed" the pre-2.90 Winamp base skin, using textures from the "Classic.wsz" skin, which was originally used on Winamp3, and the gen.bmp and genex.bmp textures were extracted from Winamp 2.90 beta.

Special thanks to Steve Gedikian for originally creating the skin.
Media Library textures seems to be "bugged" with this genex.bmp file I used, despite this is a "cool" reconstruction I did.