Most model railroaders would call this a fantasy locomotive although I prefer the term hybrid. I've taken the wheel and valve gear layout of the first prototype pictured. Next I added streamlining sheet metal in the style of the second prototype. Finally I used the colour scheme of the third prototype. From a design standpoint I haven't broken any rules, but there is no real prototype for this model.
This image is probably the main reason I find computer modeling so much more satisfying than scale modeling in meatspace. I defy anyone with even the largest live-steam model chuffing around their backyard to take a picture like this from the cab of their locomotive keeping the horizon and the handrails in perfect focus.