If you have a Premium MOC, there are some additional restrictions about what you can and can't submit. Most notably with Trademarked Terms.
Trademarks are used to protect the Intellectual Property of the trademark holder - e.g. "Star Wars". This means that if you are making a profit by selling items using the trademarked terms, the trademark holder has the right to take legal action to prevent others from using it.
Rebrickable keeps a database of known trademarked terms and will indicate when you are trying to use one.
However, it is your responsibility to make sure you are not violating any terms that we may not know about.