Looking good chris and tom. If you don't mind me making some observations and I know its still WIP but following:
Bufferbeam: I assume this isn't finished off yet as its quite flat at the moment with the lack of any rivots on it at the moment.
Buffers: I assume they are part way finished for the metalic part polished look you can see on steam loco buffers.
Main Drivers: This is just a observation from the different angles on the pictures, but I think the drive wheels are abit dark and have abit to much shine to them which is giving the illusion to my eyes that they are not sticking out from the actual framework of the locomotive they sit in.
To give a idea what I'm pointing at here is a similar angled picture:
What I noticed between the ingame pic and the real life varient is the wheels stick out more from the frame in colour/focus of attention and they also have the centre of each drive wheels in a different colour for the "rod" to connect the wheels from each side of the loco, the front bogie also has a grey lining between the spokes. Maybe that can be added to the wheels and light grey shades to the spokes on the drive wheels to make them stand out and not kinda shadowed into the underframe.
Hopefully not to critical on the comments
I'm a odd sort and like to watch the connection rods and drives spin when I'm up to speed and there is some steam locos I've had in the past where the wheels don't grab your eye focus as there to sunk into the underframes shadow and textures which can be distracting, didn't want to have a repeat here.