Seems a grey area as I read so many different answers.
Of course most pictures on the web are copyrighted and permission will need to be granted by the owner for you to use them 'legally'
But I cant see YouTube having the power to determine if you have individual granted permissions to use the pictures you have in a slide show..
Say you eventually reached the required subs / hours watched to monetise. YT will vet your channel. Are they really going to ask you to provide evidence that you have all the hundreds if not thousands of emails/letters that grant permission to use an image? I dont think so.
IMO The real concern is that an image owner 'catches you' using their image without their permission. You could be liable for claims/fines/court proceedings etc. Ive heard of some channels being fined tens of thousands for using images without permission.
Ive seen some channels state in their descriptions that they are not image owners / simply 'borrowed' from Google and if an image owner has any issues - please contact the channel for deletion/aknowledgement/compensation.
Most likely, a channel doing mostly this type of Top 10 will not be asked by YouTube to provide the evidence. Instead the channel owner will be denied monetization entirely on the reason of "Repeated Submission of Ineligible Material and/or Insufficient Documentation".
Please see my thread from a few weeks ago titled: "
If You Choose To Deliberately Use Copyright Media On YouTube" for the explanation of how this could happen. And yes; YouTube
does actually have the power to determine whether or not you own all rights you need to both publish and monetize any video posted to the site.
The real problem is that they are only choosing to do hard enforcement of this
now.