A certain portion of 3D art should legitimately fall under the same guidelines as other material on Rubberslug. If, for example, a collector of puppets from stop motion animation productions wanted to post photos of them, wouldn't that material be perfectly applicable to RS's charter?
http://www.rubberslug.com/resource/faq.aspx#3-4
"Can I upload animation artwork other than "anime"? ?
Yes, we encourage all types of animation production artwork."
That should also hold true for things like production used maquettes.
Under the explicit rule, that would exclude a limited edition maquette, as it would exclude a limited edition cel (or fan cels). Of course, in practical terms, limited edition and fan cels are allowed left and right on RS. A limited edition of a production used maquette would seem to have the same kind of connection. A statue based on animated characters is similar to some LE cels, but also has an extra degree of removal from animation, and my gut says that might be a degree too far. Of course, my gut also says an original statue by someone involved in sculpting production maquettes is on topic, so my gut is somewhat confused...
