In the end, I'd guess I've covered 90-95% of PPE's portraits. The general rules I used were 'Is the NPC part of the main narrative? Do they approach and initiate dialogue? Do they give a quest, or are an important part of one? Do they have a memorable encounter?' If yes to any of these, I would give the NPC a portrait. Some NPC's I thought too minor to warrant one, and so they were skipped. Not every named NPC that Portraits Everywhere gives a portrait to has a replacement. For this part, each portrait was carefully selected and altered to match an NPC's race, class/occupation, colour scheme, apparent age, personality, and role within the story.
