I've designed database structure for a system I'm building. Currently I chose to use a forum style (forum, thread, post) for a section which gives user content. I'm stuck on name / naming conventions since it is not a forum. I want to use basic name principals. I thought at first I'd use (category, subcategory, ...) but realised that within the (category) table I could insert a (parent) field. The (category) & "thread" tables each having their own set of fields & partnered-tables which are unrelated.

I'm stuck, and I came here looking for guidance. Any suggestions? =]

I think after reading this post three times, that you are not asking about names, but structure. And, unfortunately, if that is what you really want to discuss, you have not given enough detail to make it possible to understand the problem.

What is the purpose of your 'system'?
What are the requirements for the 'user content'?
- what actions can be taken on this content?
- what display is needed for this content?

Relational systems (most databases) don't map cleanly to or from hierarchical systems that have 'parent/child' or 'container/contents' layout, particularly if there is more than one level. If you are using a relational database, you should think hard about whether you need a hierarchical representation.

I used a CMS database structure to assist me (Mambo 4.6 Lite).