These skins are simply a mod. They might get added to the next release, but as of right now they are mods.
Saying Quadropolis is not a filing hosting service seems to be the most incorrect thing to say. Quadropolis is not meant for all types of files, but game content for cube engine games is allowed to be uploaded here. I see no reason to get so upset over this specific node. There are many horrible, and unplayable maps here, yet this is the first node that I've seen where someone has said not to post X content here. Either way, this is user made, and must be added as a mod to the current version anyway. If possible game content for the next release is not acceptable, then no maps or mods should be posted here, as these too can make it into the next release. In fact, leave Quadropolis empty, we wouldn't want any devs adding anything to the next release. We all know no one wants that...