If you want to use traditional titles to communicate your roles, Chief Executive Officer is typically focused outside the company and Chief Operating Officer is focused internally. If you want to take a more creative approach to reflect a more modern edge, you could consider calling your partner the Chief Revenue Officer and use the title of Chief Visionary Officer for yourself. You could go even further with titles like Digital Marketing Magician and Sensei, but beware of getting too cute and confusing clients and employees. Remember the most important reason for titles is to clearly communicate position and purpose, and not ego advancement. Happy to share my experience creating and running multiple private and public companies if you'd like to follow up.