I can't say that I have ever seen photos of Mt. Vernon station going that far back.
One thing to consider is, before about 1910 the right-of-way ran along (or on) what is now MacQuesten Parkway (it was then called Railroad Avenue), two blocks east of where the tracks are now. When the Harlem Division was electrified through Mt. Vernon the tracks were relocated to the embankment upon which they still run. (A similar relocation was done at White Plains at the same time.)
In old New York Central records (I've seen at the New York Public Library) there were two reasons given for relocating the tracks. 1) To eliminate grade crossings and 2) to allow the ROW to be expanded to four tracks.
Here's a map view of the station area in 1868. I marked the later location of the station with a red 'X.'
Ironically, West Street is still there, though now it's east of the station (see below):