For that thing, I was thinking about Steam-Workshop... Lots of Games do that... You can Share and Download the Images from there and use it in the Game. Steam already looks at the Content, which gets posted. Lots of People in the Community can Flag unapropriate stuff and like that you can remove then, just with the proper People online.
Plus to remove all inappropriate stuff is impossible. You can type in a Teamname... You can modify Saves to play in a complete other universe with other Teams and Teamnames.
And for Copyright, there are nowadays so many tools, you can even say, we do that behind a small paywall to put that in the game or get that pack for implementing...