Winamp Skins
Skin Making Tutorial - Part 2
You need this file, unzip it to the same directory as the other files and customise to your heart's content, then hit F5 in Winamp.
You might also want to include a file called dialogs.txt or readme.txt, for display in the Skin Browser's information panel.
More about the bmp files:
There are 16 bmp files, and here's what they do:
For ease, I copy and paste these files into my directory,
to act as templates, eg: I've put down a picture, and I can paste the images onto the picture,
to get just what I want!