You are right that it is Mark Kingsworth's design. And it is an excellent one at that. I never said that the ship was Roman's design, only that it was his IMAGE design. Perhaps that was a poor word choice on my part.
We attempt to get permission for the use of other people's art in our fan-fiction sim. As I recall, Mark Kingsworth was contacted personally about the use of this craft.
Most Trek fan artists have no issue with re-use of their material. In fact, they usually encourage it. I would! To use their material indicates the highest level of appreciation for the work that they invested in the project.
It's blatantly obvious your initial post was nothing more than a blatant advertisement for your RPG group, and one that was an epic fail at that, since you did not credit the original artist of the ship design.
Also, most artists DO take issue with re-use of their material... they spend lots of time on it, and don't need to see it ripped off, and mutilated into other purposes, without credit. This is why many of the REALLY skilled modelers on Sci Fi Meshes and other sites don't release their models most of the time.
And you only said you attempt to give credit to the artists AFTER you were caught with someone else's image... a very transparent move on your part. It means you're just sorry you got called out. You should have started out by saying "I don't know who the original artist is, but if someone can tell us, we will credit them"