That would look very sweet, but the way Windows draws the trackbars & thumbs prevents it.

Check the template images for the default (template) XP skin in SkinStudio & make your images the same size as each of those - anything bigger (or smaller, for that matter) will get distorted badly. Maybe you can get something approximating that within the confines of the limiting size, but my previous work with thumbs & trackbars leaves me doubtful - it's very tricky if you get away from the default configuration.