The amazing Fenric has just released a new free plugin for Carrara called: Insert Primitives.He is also running a contest right here in the CarraraCafe Forums with some secret prizes for the best renders using the new plugin, that allows access to 4 hidden primitives in Carrara:
-tetrahedron
-teacup
-octahedron
-dodecahedron

Head over here to get the plugin: http://fenric.com/wordpress/downloads/

Head over here to post your contest renders: https://carraracafe.com/?page_id=2022/contests/fenrics-carrara-primitive-challenge

Here is my contest render:

4primitives_inglass