In short, we don’t know what Jesus looked like because the Bible does not give us a detailed description. What we do know is how the Ancient Near East portrayed Jesus, which can be seen from the earliest images we have of Jesus.
The oldest surviving icon of Jesus is entitled "Christ Pantocrator" (Christ Ruler of All). It is an encaustic painting from the 6th century, in St. Catherine's Monastery at the base of Mt. Sinai. An encaustic painting is a hot wax painting, where beeswax is heated and colored pigments are added. While commonly known as St. Catherine's, the official name of the monastery is the "Sacred Monastery of the God-Trodden Mount Sinai" - in case you wanted to impress your friends.
Two other images of Jesus worth noting are "The Good Shepherd" and "Christ Between Peter and Paul".
"The Good Shepherd" is from the 3rd century and is found in the St. Callisto catacomb in Rome.
"Christ Between Peter and Paul" is from the 4th century and is found in the St. Marcellinus & St. Peter catacomb in Rome. The fresco is found inside a cemetery villa that belonged to the Emperor Constantine and depicts four martyrs in the foreground: Gorgonius, Peter, Marcellinus, and Tiburtius.
