Outhouses isn't a superset of this. Outhouses is for a very small subset - ie unplumbed "old fashioned" (whatever that means) toilets, and does not stipulate "public". It also has some rather bizarre requirements and incomprehensible language - but that's beside the point.
A category as described above, for public toilets that exculdes those that are for patrons of commercial establishments (malls, train stations, McD's etc), COULD ... when you come to think about it ... be quite interesting, but it would need careful thought and wording without which it could result in some downright dull and unpleasant waymarks.
Something to consider would be "converted public toilets". A small Victorian public toilet block near where I live has been converted into an Estate Agents (Real Estate Broker). Also, in Turku, Finland, there is a bar that is in a converted toilet called Puutorin Vessa (Puutori Toilet, Puutori (lit wood-market) is a market square in Turku) Their website is in Finnish: http://www.puutorinvessa.fi/files/vessa.php
and here's a review in English: http://www.theaustralian.news.com.au/story/0,25197,22523609-27978,00.html
They (in the UK at least) are a bit like public phone boxes really - something that used to be provided by the authorities for use by the public, but which are dying out.
Personally I'm not 100% sold on "wow factor" yet, but the possibility does exist.