I love this little trick and I've used it many times, since we have movie and music posters of all sizes throughout our house, particularly in family room!
My daughter is currently going through her obligatory Johnny Depp phase (well, I mean, who hasn't?) and her brother got her a really cool poster for her birthday.
On my Goodwill run this weekend, I found an awesome gray metal Ikea poster frame for $3.00! Since we always have posters hanging around, just looking for frames, I grabbed it!