Thanks for offering to follow up on this. Actually, I visited the Randolph Co., NC Library at Asheboro this past summer for the first time, and was amazed at its large genealogy collection, including Farlow material. I didn't run across much on Isaac Farlow other than what I already knew from the Farlow genealogy, but when I go back, I'll try following up some more. If there ever were a picture of him, someone probably would have preserved copies. The main reason I am hoping there was is because Isaac's daughter Ruth Farlow, my great3-grandmother, married Joseph Newlin, whose father, Nathaniel Newlin (1768-1867), lived to be 99, was a Quaker like the Farlows, and lived only seven years later than Isaac and there is a picture of him. My guess, however, is that photography was slow in reaching the Quakers, due to their modesty and humbleness, just as modern-day Amish shun photographs. Nathaniel Newlin's photograph may have been an extremely lucky find.
Also, the Farlows, Millikins, and Bullas of Randolph County have a combined reunion at Marlboro Friends Meeting at Sophia, NC, each fall. I haven't been to one yet, but that may be another good way for me to find out more on Isaac and his descendants.