Put Where I Got My Pics From In Youtube Description

im starting to post videos with a couple celeb pics in them. legitimate i have the rite to use the pics

i see some people putting where they got their pics in the description of their vids. is this necessary. if i dont when i apply for monetization will they just deny me without reason and ill be stuck with nothing and cant tell them or show them where i got them. do they just decide at their own will who they think have used pics legally or just deny them