I guess if you really wanted, you could render your part or assembly and save the rendering off as a jpeg. Then you could insert that picture on your drawing - Insert, Object, Create From File, and browse to your picture. Your rendered picture could also be a screen shot, although it would be a little less realistic than a rendering, but much quicker. Obviously this picture would not update as your part or assembly update with changes and you would have to re-render and place on your drawing again. Not the best solution but it techincally is possible to get a textured view of your part or assembly on your drawing. I would advocate putting in an enhancement request for what you want.