Microsoft is planning to bring a major revamp in the aesthetics of the Windows 10 Skype UWP Preview App that it released to Insiders in Fast Ring with Build 14316. Some leaked screenshots (thanks to Gustave) partially reveal the new look and feel of the app including a new Dark Theme. Check the screenshots below.
The Skype UWP Preview app has been quite bare-bones kind of app till now and it was expect that Microsoft will make it appealing by adding features and improving its design.