The VLC team continue working on the Windows Phone version of the VLC app. The release notes say there are background audio fixes and video playback fixes, since I last used the app last it seems background audio playback has been added to the app. This means you can start playing music with the app and then switch to another app and music playback continues which is exactly what you need for a music player.
You can find app in the Windows Phone Store.
VLC 1.0.7 changelog: UI bugfixes, background audio playback bug fixes. Should no more freeze on x20 devices when playing video.
— Thomas Nigro (@ThomasNigro) January 14, 2015