Whenever you own a company, it's beneficial to make yourself look professional, but not to seem overpowering. Puffing yourself up too much is just ridiculous, because the average client will see through it.

In my company, I usually just refer to myself as Publicity Manager, and in correspondance, sometimes Owner / Publicity Manager. It's worked nicely for me so far, and I think people assume you're more personable when you don't "brag" about being top dog.