I can explain the physical sky problem really easy, do I would need a model of a nice house or building to explain it in a picture tutorial. Anyone got one laying around, I would use it solely for this tutorial.
Vignetting I can explain without a problem, it will be covered in my main tutorial now you mentioned it. (still waiting for some renders???)
As for the grass I can also show you how to do that, I will answer these three questions as one as soon as I can get a decent 3d model from a nice house or building. So anyone got some laying around?
General foilage and grass will be explained in the same tutorial I will be making for jenujacob, as for camera angles those will also be covered in the big tut.
Though I need resources before I can answer any of these questions, renders (PR) and a 3d model of a nice house or building. I have seen several on these fora, perhaps someone would like to contribute one to this tutorial, it would be appreciated.