I think that stuff like mystic trees, campfires and pet statues would not be allowed simply because some people will be fooled into thinking they are RARES when they arent bec ause they look alike.
However, as a vendor of rare pet clones, I can tell you that my copies are legal because when you buy pink poodle or purple turkish, you can only buy them caged. However, these arent caged and clearly labeled as "stuffed animals." I never had one complaint yet. Heck, if somebody does buy it from me thinking it was a real live pet, I will gladfully refund their money. The whole point if not to fool people. If a cc is marked as custom content and not carbon copy, I dont see anything wrong with that.