I've been making some improvements to the skin system for awhile now, so...
If you have a MediaWiki skin you've built, feel free to bring out it's source code. Currently most of the few custom skins that exist are floating around the Internet, and they are various degrees of out of date. Bring up the source code, and I'll look into committing the skin into svn and cleaning it up stripping away the boilerplate.
I would LOVE skin designs right now. If you've got a nice idea for a skin feel free to mock it up and post the mockup images for it. If it looks interesting I'll consider turning it into a real skin, ESPECIALLY if it break our de-facto traditions on what makes up a wiki skin. Our rigid skin structure is one of the big limitations of our skinning system right now, skins that define things beyond the current restrictions are good examples needed while we break open the rigid structure of our skins.