This has been something I always wondered about, but wasn't sure if there was software or something that would allow me to modify this.

I have a very large episodic movie library in my itunes. I love coverflow, and these movies are converted for use almost exclusively for my ipod. My question therein lies, is it possible to make it so that itunes reads my set 'poster frames' as album art and not as movie posters? I don't like the large black void in coverflow that would otherwise accomodate verticle movie posters when all of my poster frames are square and horizontal.