yeah, you do need permissions then, It's a nice idea, but if you put 'Something' from you self in there, like the wb skin, than it would be easyer, I am sure if you mail people to use their skins they will give you the permissions. And if they do, in the comment of your winstyle put the links to the used skins.

(how ever you can put togheter your own desktop and upload it in the screenshot section, where you can post links to the parts u have used...)

It is common courtesy, when posting a Winstyles Suite, to list the author's names and the names of the works.