Hi,
You can use Krypton controls from Component Factory:
http://www.componentfactory.com/windows-forms-products.php[
^]
It comes with themeing out of the box. Latest edition is from 2012 but their forum is alive and you can find many useful tips there. I still use this set of components in one of my old projects. There is an additional pack called AC.ExtendedRenderer.Toolkit from http://angelonline.com but I see that website is unavailable today.
Krypton.Toolkit is for free for personal and commercial use.
Cheers!