[gus_massa]

I was confused by the carrousel at the top and I though the backgrounds include the photos of the actors. But IIUC the backgrounds you give are in the second row.

What is the license? If I use one of this backgrounds in a talk, can I upload it to YouTube?

[sanketn]

Fair point.

Yes, please go ahead use it in the talk, upload on YouTube and use it wherever else you want :)

[gus_massa]

The page does not specify the license, so people will be afraid of using it.

You should read all the possible licenses to ensure that people can use it as intended, but can not use in unexpected ways.

For example sometimes people choose CC0, and then get angry when other people redistribute it without attribution.

I suggest to take a look at https://creativecommons.org/share-your-work/ and once you have a rough ideas ask here for advice.