hi,
No invisionfree is only a hosting service where you get to invision power board (probably outdated but patched for security) for free
vbulletin is a complete forums package once you are licenced you can download skins here and see how other people do it.In the ACP (the vbulletin admin control panel) there is a thing called style manager from there you can manage the whole design on how your forums will look
a known vbulletin skins site is
www.vbstyles.com or
http://www.cinvin.com/products.php?do=products&catid=4
just to name two sites
ciao