I am playing with Silverlight 4 beta a lot at the moment, and one of its best features is the new Implicit Styles. This means that I can design a Silverlight theme for all the controls, and all developers have to do is include my supplied Resource Dictionary and all their controls will be skinned.
So I’ve made a theme called Blackspike, please download it and try it out on your project. Let me know if you find any bugs in the comments below.
Download the Blackspike Theme for Silverlight 4 final