crap, I wish I knew more about 2D rendering/editing, otherwise I could help, my Photoshop skills are amateur-ish at best, but I usually do 3D renders in programs like Carrara 6 & others, where my knowledge is a bit more better, have rendered images as large as 6400x4800 LOL...
but anyways, I'm keeping an eye on this thread for others to post too, as I'd like to know how to use Photoshop (CS2) or GIMP to enhance an image like your talking about, especially since DVD resolution is considerably less than the res's your talking about, how to capture a clean image & increase it with out getting all pixelated or blurred or even clean it up to work right in the overall image.