had a little chat with @trevor about this feature, initially as a plugin, but after digging around the topics source a little bit, it sounds like NodeBB core maybe a better place for it.
with your blessing, i'd like to implement this feature (PR), but I would first love to hear any specific sub-features, design opinions or whatever else you have in mind on this.
My major concern is where to store the images urls, on the topic objects in the DB? or on separate meta object?
if the decision remains a plugin for this, we're going to need few hooks for the topics create and getTopicData, which I will PR as well, but IMHO this feature sounds like core.