You may be interested in this wonderful article [1] about how these and many other unusual symbols ended up in Unicode. I personally had never considered how much of an issue including flags could be. Quite an interesting discussion around it on HN as well. [2]
Theres not anything seedy about a love hotel. In Japan sometimes it's nicer for couples to go there rather than try and have a romantic evening in a tiny 1 room flat on a futon.
The snowman is an old meteorological symbol for snow. Predates Unicode by decades. I assume it's because a snowman is easier to render by hand than an actual snowflake. (Or like how rain is symbolized not by trying to draw recognizable rain itself, but by an umbrella.)
http://www.fileformat.info/info/unicode/char/2603/index.htm
After that the only one to shock me was "Pile of poo"
http://www.fileformat.info/info/unicode/char/1f4a9/index.htm