Should this be tagged nsfw?

By my own standards, no, but lemmy as a whole seems to be kind of prudish. Maybe a presenting foot pose is over the line for them?

I personally have no problem with it but I can see how other people might have one. Then again, if we go with “nsfw -> might get troubled looks in office” then a big part of the posts in the Moe communities would need to get marked xD

You already changed the marking, so I would say leave it as is. But similar images don’t need to get marked except if they also get reports (form multiple different persons).