Okay, according to the NPC section of the rules...
“Like characters, NPCs have one information text field that their manager, supervisor, or owner can edit. This text field can be used to display a job title, military rank, or other honorific distinction.
Similarly, NPC pictures can be changed. A range of possibilities, based on the NPC race is proposed. Additionally, each faction can propose custom pictures to be uploaded on the server. These pictures are then added to the available selection for the concerned faction. Each submitted picture must correspond to a given race, be 100x100 pixel in size, and under 7KB. Submissions are accepted in the Art Team Public forum. Note that when a NPC with a custom faction specific picture is made over to a third party, then the picture is automatically reset to a standard generic image.
- Rules ”
However, when I look in the exchange CP section, one of the images for custom images is NPC. So, is it possible for someone to exchange CP points for an NPC custom image if they are not a faction?
Using the CPs you've earned or clicked, you can add your own image to an NPC.
Edit: [Removed some content as no longer necessary and could have been considered inappropriate]
From my reading of the rules, I believe that Factions can propose a set of custom images that may be used for NPCs within the faction. For example, a faction could submit images that were wearing the same uniform. I've not been involved with that so don't know for certain.