There are several synonyms for the phrase "on the face" which can help add variety and nuance to your writing. One possible alternative is "facial," as in "a facial expression." Another option is "visage," meaning "the face or facial expression of a person." "Countenance" and "mien" are also words that can be used interchangeably with "face," referring to someone's facial expression or demeanor. "Physiognomy" is a more formal term for the overall appearance of a face, while "aspect" can refer to a particular feature or expression. Using synonyms effectively can help you avoid repeating the same words over and over, enhancing the richness and variety of your writing.