... so that they don't demand an authority censors the choices...
Good luck with that. At the same time, it is worth reminding that the worst form of censorship is self-censorship.
... it is inappropriate in the US workplace to look at explicit content...
For that to become an issue, there has to be a pattern (of repeated behavior) and intent to create a "hostile work environment." A few seconds before you close the thread is not going to create any trouble for anyone.
Ultimately, if you are so paranoid or if you work in such an ultra-sensitive environment, stop frequenting photographic sites, because, you know, they tend to contain... photographs. Better switch to CNN and watch to your (and your co-workers) heart's content idillic scenes from the latest carnage by suicide bombers around the world. That, I gather, is accepted as quite appropriate?
Even better, get off the chair, walk around, get some fresh air... good for circulation, you know. And improves productivity.