WPF is extensible and much popular.
You should skin controls yourself, may be using Expression blend.
You can style, change templates etc. for each style and hence can create a new look and feel for each theme to the user.
I have written an article on how you can make a style pluggable:
http://www.abhisheksur.com/2010/06/pluggable-resource-for-wpf.html[
^]
You can try that too.