Per the recommendation of several guild members I am using Gimp to build a map for a Star Wars RPG session. I am working on a space transport which our group selected out of one of the sourcebooks. After several adventures we have customized the starship to our personal tastes. Therefore, I am using the sourcebook's "stock" starship layout as a starting point and modifying the layout per our group's customizations.

My question is this: Am I allowed to post this work on the forums for comment?

I am using a Star Wars RPG sourcebook drawing as the template (West End Games published the sourcebook, but has since lost their Star Wars franchising license). I am not using any symbols or artwork from the sourcebook other than the general shape of the ship and the general layout of the ship. I am concerned that this may violate the posting policy with regards to plagiarism since I am effectively "painting over" parts of the original map (and then adding in my own work to customize the map).

I would appreciate guild members' assistance and comments on the map but I do not wish to violate the posting policies. Could a moderator please advise me in how to handle this?