Hi, I'm new to this also, but just to point out the differences, CSS deals with the look of the site, these come with the templates you install, anything with .php refers to actual coding of the site and its functionality. I think for now it's probably best just to use the standard images/large/bracelet_LRG.jpg instead. At least it works and i'll keep working on how to get subfolders working for you !
Until then !

Cheers and have fun !
J#xx
(Scott Perry)