UPnPlay is an UPnP/DLNA client that can be installed on Android devices from here. This app is primarily designed to play the music from your UPnP/DLNA media server. It has a simple music player UI with album art, playlist and the common operations (next track, shuffle and repeat). It can also be used to play video files, by using an external renderer.
The main advantage of UPnPlay is that it is free, has no ads and no restrictions. There are other free media clients that have far better UI and features, but they all come restricted (like playlist size or the number of items that can be played) until a Pro or paid version is used.
I primarily use UPnPlay to play music. The UI is rudimentary and clunky. But, do spend a few minutes pushing the buttons and you will fully understand the interface. It is actually quite intuitive once you learn it.
The only missing feature was that I cannot add all the files recursively under a root folder to the playlist. I created a workaround for this by creating M3U playlists for those directories and placed them in my root music directory. UPnP/DLNA supports such playlists and the files in it can be added in UPnPlay to its playlist in one touch.
Tried with: UPnPlay 0.0.93, Android 5.0.2 and Moto G2 (XT1068)