When you make something for a community or group, unless you have an agreement that you keep full rights, the rights get transferred to the owner of said group.
Seeing as all OC logos were made for OC, then they belong to OC. Same with Cosmos FM.
The rank image was temporary so that it would show up and not look like total shit, and the logo is infact still property of Cosmos FM.
Oh, and to clarify: when Rofl bought the gamemode, it included the content as well, and seeing as the logos and shit are part of that content, they became property of CG.