Attached Link: http://www.runtimedna.com/messages.ez?forum_id=28&Form.ShowMessage=76990

If you are using a background image as opposed to a textured prop, then you will be unable to cast shadows onto the background picture directly. There is a way to get shadows onto your background picture in Poser5, that is by applying the shader in the link I've posted to the ground plane. One other thing, do you actually have the ground plane enabled? You could also try applying your picture to something like the Infinity cove prop in the freebie section at www.runtimedna.com and that way shadows would be cast onto the ground.