Covered wagons bring a genuinely railway feel to any freight consist: they don't seek individual attention, but they give the train structure and a sense of purpose.
A covered wagon set for coherent SNCF consists
This LS Models 30504 set lets you add Murphy UIC Europ SNCF rolling stock in H0 scale, with the advantage of building your consist as a group rather than as isolated pieces. On a layout, it works well in epoch III freight trains, whether running or standing in a yard.
Expanding your freight fleet
Its real value lies in the overall effect: several covered wagons help build a more convincing consist, with that regular-traffic look that makes a scene feel less improvised.