I can tell you that many Hubbers use photos that they strictly can't use but they may be allowed under fair use. HubPages is a US company (right?) so it should be covered under US fair use law. But I also see people using photos that are definitely not free: the author of the hub does not own the copyright and the content has not been licensed under a free license. I'm just saying that just because others use great entertainment photos does not mean they are on the right side of the law when it would be challenged.
Having said that, I'm also using flickr.com (use the advanced search for Creative Commons photos) and http://www.publicdomainpictures.net/ which you can use commercially and just a link to their website suffices.