You can use some stock photo sites, like Stock Exchange or IStockPhoto to find royalty-free images, but you do have to agree to the terms of use, contact the photog most of the time, and you might have to pay for them.

If you use someone else’s image on your book cover, you run the risk of not only being sued, but possibly costing you lots of money by having to redo your book cover and not being able to sell any of the ones you have printed and paid for.

Always be sure to properly get licensed images to use or take them yourself. Never use images you find on other sites or in Google for commercial use at all.

Sorry.

(The one exception might be if you were doing it as a parody of these characters. Parody is protected under fair use.)

ILikeFilms, yes, it’s okay to use the names of the video games. You can have your characters talk about characters in the games and use their names too. I wouldn’t use them as a basis for plot though, like fan fiction. For example, you wouldn’t want to do a story based in the Pac-Man universe, with Mr. and Mrs. Pac-man as the main characters, and the ghosts as the bad guys, etc. That’s fan fiction, sort of, and it’s usually okay for fun, but not to sell commercially without permission. But to just have your characters playing video games or talking about them is fine.

As for using elements from movies… that’s a tough call.

Now, if you have two young boys that are playing outside and one of them says, “This stick is my Star Wars Lightsaber! Fight me!” Something like that is probably okay, because you give credit to the Star Wars element and the boys are just playing around. But to use a ‘lightsaber’ in a science fiction novel that has nothing to do with Star Wars, probably not a good idea. I’d recommend giving your weapon its own name.

Hope that helps!