Sorry for any confusion, @jrox141. Great question!
To clarify, as a Premium subscriber, the background changes with the album art as the songs change during your listening session. This an intentional feature of a feature of Premium. With free and Plus, the background remains the same. At this time, the ability to change the background manually isn't a feature.
The feature request can be found here: Ability to Change Colors on Now Playing Screen
Thanks so much for being a part of the community!
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