I have a feeling the real issue has little to do with NSFW but more to do with “don’t let the boss notice I’m doing personal stuff on company time.”
That is, without images a page would look more “technical” and less “social”.
For example, why would the IT dept. block Facebook? AFAIK Facebook removes NSFW content as soon as it becomes known about.
My bet would be that the IT dept. has also blocked Solitaire on the company computers as well.
In other words, the IT dept. feels that any “down time” while on the clock should be spent on work related activities.
Again, I don’t feel that the Discourse Core code is the place for an optional “deception mode” feature.
But I would have no problem with a plugin being used for this if doing so was considered important.