Strange picture on my lock screen

[Ilfracombe]

My wallpaper, the image behind the app icons, is fine, and as I chose it. However, whenever the lock screen comes up, there is a strange graphic, which I have discovered is a segment of some artwork for a podcast. I never chose this artwork, and would like it to go away.
Why did my phone choose this piece of artwork, and how can I get rid of it?
thanks

 

[GlennTX]

some podcast apps put the podcast art on the lock screen to remind you what you are listening to.
On my N5 it goes away when I close the podcast app (pocket cast) or finish the podcast.

 

[Ruben_915]

I had a frame from a YouTube video stuck as my lock screen wallpaper until I turned it on and off. I think it's a bug in Lollipop with video playback. It happened when I was back and forth between the home screen and the YouTube app. I've heard of this before but didn't read too much into it since it hadn't happened to me, wish I did though, I saw it somewhere on a forum here.

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