There are all sorts of ways to get backgrounds in Poser scenes, but we'd need more information as to what you are doing. For interior scenes, you can use digital photos or renderings (jpgs) slapped onto squares, coves, cyclorama planes, etc. or use a model of a room stocked with furniture (better since the shadows will fall more convincingly). For exterior scenes, you can use photos and renderings as above, any of the small realmz from RDNA, or a terrain prop with a background sky if you need something more vast. For rendered backgrounds, you can make your own with Bryce or Terragen or Vue, among other programs. You can download many free backgrounds or buy them in the Marketplaces. You are the only one who knows if you are making the traditional NVIATWAS or going for something exotic, fresh, original. If you are rendering an ill-fated polar expedition, you'll want snowy landscapes. If a dryad, you'll need a hardwood forest. If a pin-up, a luxurious satin bedroom. We don't know what to recommend. Yet. ;^)