I'm with 920walker -I believe- that data usage can and should not be an issue for playing music that is stored on your phone or SD card, including his or her reference to images. I have >50gb of music on my 128gb card, two-thirds of which is downloaded Zune/Xbox/Groove Pass or subscription music. I can turn off cellular and Wi-Fi, and ALL my music will still play as normally -including images, and continuously as with the wireless connections on. So, even subscription music does not require any online connection. That is the beauty and logic of the Groove subscription: music is downloaded, stays, and plays continuously until you delete it. And, all your phone-stored music will keep playing anywhere you go as it would on a dedicated music player, even without any wireless connections.
Rid08..., I don't know anything about Android, but Groove does not require streaming anything to play card- or device-stored music. I can testify to this running Groove on my 950, and on my upgraded-to-Win10 Surface Pro 2. (BTW, this was also the case with my Lumia 1020 running Windows 8.1.)