You can get the whitebox.dsl extension from the repository and use that to customize your fluxbox style. Also here is a great page to help you make your own. It covers everything you will need to know to get started creating your own style.
http://www.fluxbox.org/docbook/en/ht...style-man.html
Another option is if you like one of the current styles that comes with DSL but just want to tweak it, you can find these in /usr/share/fluxbox/styles and the backgrounds in /usr/share/fluxbox/backgrounds. When you have created your file, you should place it in /home/dsl/.fluxbox/styles and it will show up in the styles menu.