锦上添花 (jǐn shàng tiān huā): lit. add flowers to brocade; fig. to give sth additional splendor; to provide the crowning touch

jǐnshàngtiānhuā

lit. add flowers to brocade; fig. to give sth additional splendor; to provide the crowning touch

Flowers on brocade: a nice addition to something already fine. Its pair is 雪中送炭.