So I've been doing the research I mentioned previously and there is a surprising abundance of public domain film footage on the internet. I've been scouring The Internet Archive and there's just a mess of videos, audio files, and still images (not to mention The WayBack Machine, which allows you to look at long dead websites). Sadly, the large amount of available material almost makes the job of creating film-poetry more difficult because there's so much to sift through before you find something that will work for your poem. I suspect what I need to do is find some footage that speaks to me and write around it rather than trying to find footage that fits with existing poetry. At the very least, that'd be a less time consuming way of creating.
I've only done one film-poem before, and I actually dubbed it a digital elegy back in 2007. It was an elegy I wrote for my grandmother and it combined still pictures of her along with various musical tracks and some random footage I filmed myself. It took forever, but the end product got me an "A" on my Senior Project for my undergrad degree, so well worth the time. However, I really would like to get this process streamlined so I'm not taking months to do one project. A couple weeks, at most, is my preferred timeline for producing a single film-poem.
As to subject matter, oi, whatever happens to pop into my head and inspire me at any given moment. ;p As they say, the sky is the limit.