Overall, having the correct letter format will guarantee people that they can have the upper edge against other job applicants. All they need to do is to keep it clean and unique. There is no need to have a very extravagant cover letter. Just indicate all the essential things needed that can help them to get the job they need.
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.