I haven't voted in the poll because there's no "choice E: A, B & C" category. The best I've seen have been combinations of a painted sky with printed structures and/or photos applied to that.
Personally, I've used a painted backdrop, but wasn't all that satisfied with it as the layout height was too low and the backdrop was interupted by windows.
I do want to mention a thought relative to the poll, that of freestanding backdrops on island-style layouts. In planning a small layout I have often considered using a backdrop down the middle lengthwise to effectively separate the layout into two scenes, which, because of the backdrop, can be visually very different, e.g. city on one side and country on the other.
But my wife, whose artistic opinion I do value (yet not always agree with...) has a strong dislike of the 'sky wall'. We've had some good conversations as I've tried to understand what it is exactly that she dislikes about these freestanding backdrops. Of all the photos I've shown her (not closeups, but where the layout itself is shown with fascia, backdrop, etc.) she has yet to find one where the backdrop is acceptable. Even those along the walls. Anybody else feel this way? (or have a spouse that does?)