First of all I want to say THANK YOU to Menards for the great releases so far- and no I am not kissing up... just thankful for what they have done for our hobby.
I am told that the Evans 5277 box car is the most common type used in North America. When searching for one to illustrate this post- I came across this livery that I feel is quite attractive and would appeal to many modelers.
Of course there are many other liveries that would be colorful and popular- a search for 'Evans 5277 Boxcar' yields many ideas...including this RailBox 'graffiti' car. Perhaps not for all tastes but it might be an interesting addition to a modern consist.