yeah the admincp style section in conjunction with the templates are the two vital parts to understand when making a style... if in the admin cp where the style section is at if you go down to the listing of the banner and buttons you'll see a list of paths to the images folder... now within the images directory create a new folder and then replace all the image/ parts in the style section with image/{foldername}/ and that'll replace all the vbulletin default graphics with the ones that you make... i personally don't make my own styles i have my designer do that

regards... hope that helps...
g-force2k2