I have never been a fan of the plastic looking decks that come with most stock flatcars, then again I can't think of too many others who like them either?
I have had decent luck painting them to resemble wood decks, not a hard process and not too involved.
I had moderate luck with them, nothing outstanding to write home about but they are better than looking at the plastic painted decks that match the carbodies.
The hardest and most time consuming part of this was getting them sized to fit the cars I wanted them applied on. As far as printing them, the color will vary a bit once printed and the black ink tends to have a bluish tint, so I tried printing a few on some old Manila folders that I had in the office, which did change the tint bit.
The next step was to weather the cars before gluing the decks on. For glue I tried using some of the Elmer's Glue Sticks for application, which seemed to work pretty good. Although on some of the cars they have little spikes on the surface that need to filed down so the prints can make good contact.
Once the glue dried I gave the entire car and decks several light coats of Dullcote to seal everything up. I'm not sure I'll do this to all of my flat cars? But it does give you a nice variation to the painted ones.