I know of only 2; and RailPictures.Net seems to only have saearch engines for locos, not passenger cars.
If you are looking for steam era freight car prototypes, you could also try the Steam Era Freight cars site http://www.steamerafreightcars.com/gallery/gallerymain.html
rrpicturearchives.net You can search by reporting marks, car type, location. I personally have uploaded more than 2000 freight car pics to the site. It is a great reference.