We Orthodox have a good idea of Our Lord’s appearance because of the agreement between the Palestianian school of iconography and the Icon-Not-Made-by-Hands preserved first in Edessa, then in Constantinople for centuries. All Orthodox iconography of Our Lord is based on those sources, just as iconography of the Theotokos is based on the icons painted from life by St. Luke the Evangelist.
I have a few books on the Eastern Christian icons and have seen the famous icon based from the one in Edessa.