You do not have to worry much about being a copycat if you do not find the most unique cover letter format in town. Just be sure that the contents of the letter have a clear and definite direction. This will bring about a good flow in the contents of the letter.
Your cover letter format is very important to your success. With a high quality motivation letter, your chances at getting an interview will dramatically increase. Don't take shortcuts. Pay attention to both what you say (content) and how you say it (format). Your efforts will pay off in your career success!