I don't know about rendo's, but an image map of a procedural should be ok...you will likely need to do more work and using components in carrara to create an image should be fine...that is standard in all 3D licenses. If not...well that gets confusing and please show me. Many of the presets aren't that original anyway. The competing product thing is different. Image maps seem safer for things like this tho. Likely you will not just pop out presets...probably wouldn't look too good anyway and wouldn't go over well.

No need to think outside the box....
    Just make it invisible.