This question comes under the heading of Intellectual Property rights.  You want to protect your designs through copyright. Understand that you always have a copyright on original works that you have created even with out filing a copyright with the government.  But you are smart to want to protect it from the get go so I would contact an attorney about having your artists that are helping you to bring your designs to life sign an agreement as to the issues.  Also discuss the issues of trademark, licensing and patents and when those agreements and registrations should be considered in the process and as your works become a reality and actual commodity.  Good luck.