The modern idea is that an angel's face is sweet, cherubic, and blissful. Yet the truth is that angels have their faces constantly focused on Jesus. Angels "fix [their] eyes on Jesus" (Heb 3:1). The angels worship Jesus, but also are in a state of constant focused attention on Jesus. Angels are messengers from God who wait for a message from God to deliver or for a command from the Lord to execute. Angels center their entire existence on Jesus (see Jn 1:51; Mt 4:11).
Angels are always at the wait. An army of "more than twelve legions of angels" stood ready for instant deployment to rescue Jesus as he was about to be arrested in Gethsemane. Jesus noted specifically that these angels were ready "at a moment's notice" (Mt 26:53). The obvious conclusion is that these angels' faces were fixed on the hand of almighty God, completely armed and totally prepared to enter battle upon command (see Ps 123:1-2).
St. Stephen, no doubt, was worshipping God as he sat in the crossfire of the trial by fire in the Sanhedrin. But His face was like that of an angel, with eyes focused on the Lord. Though the members of the Sanhedrin fixed their eyes "intently" on Stephen (Acts 6:15), Stephen's eyes were on the Lord, not on his dire circumstances. Stephen looked to God above in worship (Acts 7:55), but he was also looking to the Lord to see if he was to deliver a message, much of which he delivered in Acts chapter 7. When Stephen was being stoned to death, he continued to look at Jesus, this time at the crucified Jesus. Stephen quoted two passages of Jesus crucified as His final words (Acts 7:59-60).
Have the face of an angel. "Fix your eyes on Jesus" (Heb 3:1).