Hi, I love FDM's GUI just the way it is But, some people may want to customize their own GUI. How about using QT Framework to build a new GUI?: http://www.qt.io/download-open-source/ I think it would be a great solution.
Also I created some skins for the current GUI. Will you have a place on the website for people to upload skins for sharing?

What FDM version do you mean?
1. You can create your own skins for FDM 3.x. They are limited in features, but thanks to that FDM is fast and small. You can call it "classic GUI" and it won't be changed in FDM 3.x AFAIK. You can upload skins of your own design to any file hosting service and post download links here, to Custom branded versions subforum.
2. FDM 5 uses Chromium Embedded Framework for GUI. There is no reason to move to another huge and complex framework. It may take more than a year to get working app with no guarantee of success. Do you know any programmer working with Qt framework? Or maybe you are willing to port FDM to Qt, aren't you?