Building a new template
Make a copy of an existing template
You'll want to do this in order to be able to upgrade to newer versions of VLW without losing your template modifications. Make a new directory in templates. Whatever you name this directory that will be the name of the template. The choose templates tool looks for templates in the templates directory. I will sometimes call templates, themes. Same item, different name.
The big changes will all happen in the style.css file. I'd recommend printing a copy of the template box layout that appears on the Templates page, and a copy of the style.css file. If you speak CSS this should be enough to get you started on making a new template. If you just want to alter some colors or fonts, find them in the CSS file with the name of the area you want to change. Syntax is pretty obvious. I like fluid templates so that's what most of the VLW themes are built as. If you prefer fixed it's pretty easy to modify the contents area to be fixed width. The nav area already is fixed width in most cases.
If you build a nice theme consider sending us a copy and we'll make it available to the VLW using world. Thanks! Just make a zip file of the directory containing the theme. It should unpack into a single directory, whose name is the name of the theme.