First of all, a premise: I refuse to believe I'm the only person on the planet that bought GalCiv3 through GOG.
So, since we cannot have access to Steam Workshop, I've decide to open this post to create a hub where we can share our ship designs with the community. Everyone can post here his creations, just place them in a zip file, put it on an online space (example GoogleDrive) and then post here a link to download them.
To start this bazaar, I share with you my first set, my Alternative Terran Military ship set, which you can find here ---> https://www.nexusmods.com/galacticcivilizations3/mods/123/
Of course, Steam users can also contribute if they want, any new design is more than welcome. 
Happy sharing folks!