A lot of companies apply very large logos to their name tags complete with tag lines and even weekly specials. Then they put the wearer's name where they can fit it. This makes the employee feel like a walking bill-board.
The name on the name tag should be the largest. Design your tag so that the person's name can be seen and read from 10 feet away. Your corporate colours can still show through and as the customer gets closer, your logo will show up. In most cases, your customer already knows where they are!