Why do I have a picture on my lock screen I didn't choose?

[AC Question]

Hello. Suddenly I have a picture on my lockscreen (Galaxy 5) that I did not put there. I don't even have the picture on my phone. It just appeared after I was listening to some songs of this band on youtube. and now It is there. Any clues?

 

[the tall guy]

Hi, is the wallpaper the band you were listening to on YouTube? was the wallpaper visible while the song was playing?