For me NSFW is something that can get me fired if somebody sees it on my screen during working hours or something that can put the consumer of the content at risk, like gore images making hemophobic people faint. I can see how this image can be a bit disturbing, but I don't think a piece of leather should be censored, as it dilutes the meaning for the tag too much.
I'd then click on something NSFW thinking there is just another piece of leather with feathers under the tag... I don't think I need to explain this one.
Systems built on unspoken rules break outside of isolated communities, considering this is very much a global community, I doubt such a system would work in the first place. Would be actually cool to have various degrees of warning tags to then choose on the client side what to unblur automatically and what not to, though.