I've posted this on other forums, but I thought I'd pass along the resource here as well:
I have worked in the retail furniture industry for the last 5+ years and one thing we have always had in excess is STYROFOAM. LOTS AND LOTS. I hate seeing literally hundreds to thousands of cubic yards of the stuff get thrown into a landfill every year (some call me a tree hugger
). I've always wanted to find a useful way to recycle the stuff and it just occurred to me this could be a small way to do that. We handle all kinds of sizes and densities. EVERY retail furniture store will have this stuff coming out their ears (I've actually coughed the stuff out of my lungs before) and would be more than happy to give it away for free.
I think its absolutely ridiculous that people have to pay for the stuff when its so readily available for free. If you want some, just go to your nearest furniture retailer (Ashley, Macys, Furniture Row, mom and pop shops, etc) and ask them where their warehouse is located. A lot of stores will warehouse in-house or have one close by that you could visit and take some off their hands. I regularly handle sheets as large as 4' square and up to 1" thick as well as bricks and oddball shapes. Some is quite dense too.
So if you're looking for a place to find free background material (that's why we DIY right?) ask your local furniture store and I'm sure they would gladly fill your car up with the stuff.
If anybody is in Eastern WA (Tri-cities, Spokane or even NE Oregon) I could personally hook you up. Just PM me and I can arrange to get pretty much whatever you'd need.