As a meteorologist I am afraid to say that I am in danger of getting all nerdy when it comes to clouds, skies and lighting.
Sorry, but I just cant help it.
Out of the three 'photoshopped' products, the second one by Andy stands out as being the most realistic, although Artizen's first one is almost spot on as well. However, the lighting on that layout is quite unique in many respects in that it is almost all natural and therefore varies depending on the outside conditions.
Tim's third photo is a great illustration of that, and care has to be taken when looking at the original. See how the shadows are almost horizontal across the locomotives, and from a Westerly direction (when imagining the real thing). This suggests an evening scenario, and I'm afraid the clear blue sky with a few bits of shallow Cumulus are not typical of that time of day.
I apologise for being so pedantic, and I am not making a criticism of anyone for anything - but with a layout such as this I feel it is worth making the extra effort to get the sky right.
Sadly, my Photoshop skills are zero otherwise I might have a go myself.