Microsoft has updated both versions of Skype that run in Windows, which is to say Skype for Modern Windows and Skype for Windows desktop. The former picks up new options for managing your availability (at least "new" to that app), while the desktop version unexpectedly gets a more attractive chat experience.
The update to Skype for Modern Windows was announced via the Skype Garage & Updates blog. It includes the following new options aimed at helping you manage your availability:
Invisible. With this availability option set, you will still receive incoming messages though your contacts won't know you're there to receive them.
Sign out. This blast from the past signs you out from the service and prevents any notifications.
Skype for Modern Windows requires.1. Since Windows 8.1 already includes Skype, you should just get this update automatically.
As for the desktop version of Skype, I don't see any blog posts about this update. It's likely you're using a 6.14.xxx version of Skype if you're using Skype for Windows desktop, but what you need is 18.104.22.168 or higher. So you can download the latest version of Skype for Windows desktop. When you do, you get a nicely restyled chat window with conversation balloons. I normally can't stand that kind of thing but it's nicely done here.
Are there other new features in Skype for Windows desktop? Could be. Let me know if you find anything else.