There are some that love to go with more traditional pirate wench costume and common couples Halloween costumes. There is nothing wrong with that if that is what you want to do. You can go with any famous couples throughout history. Some like to go with king and queen, or Anthony and Cleopatra.
You can go with Adam and Eve if you like, or perhaps Tommy Lee and Pam Anderson are more your speed. Elvis and Priscilla can be a popular choice, along with couples Halloween costumes that are of current celebrity couples. This can be political, athletic, or other celebrity couples as well.