Can I use copyrighted posters in my short film? Would that be the same as using someone's music? I'm assume it is but I need verification. I'm shooting a kids room and I need posters, what can I do for alternatives? Thanks.
Make up your own posters in Photoshop/Corel/whatever, have them printed to the right size by a service bureau, and you're set.
Don't use anyone else's copyrighted or trademarked material, if you have any expectation of your project having commercial appeal. You'll have to sort out clearances, which can be a magnificent pain in the ass.
There aren't many posters in this set, but there are plenty of fake labels to use in productions. They might be of some use to you in this (or future) productions.