Why are you doing yet another 4-8-4 (and not a particularly good-looking one at that), when you could re-create one of, if not THE most iconic steam locomotives ever built, the NYC J-class Hudson?
Looks are a highly subjective quality.
I happen to belong to the "beefier the better" school of locomotive appearance.
I much prefer the bulkier J3 Hudsons to the original J1 locomotives, for example.
I also prefer the late PRR look with cast steel pilots and chin plates as opposed to the as-built, daintier appearance of the K4s Pacifics.
There is nothing wrong in my eyes with the NYC Niagaras, with the possible exception of the googly-eyed appearance of the twin sealed beam headlight. I much prefer the old-school Pyle headlamps that they carried when new.
The Pyle National twin-sealed beam headlights went into production in 1949, so the Niagaras were in service for 3 years before they were retrofitted with the new headlights. The air horns were also added after the engines had been in service for some time.
I also love the UP 844's looks.