Its hard to say really..everyone has their own idea of what ratings should be, what is art, what is acceptable to that, and it ranges to such a great deal that its not exactly a science to nail it down.
The top pic is of a statue, something that is in the public view....dont think there is anything wrong with that myself however, many uptight Americans in particular would find great offense in that.
Ditto the second however now that goes into the realm of art and artistic expression...which leaves it more wide open for being something that should be rated in some way.
I find it silly myself but, you know, Im not uptight about it either.
Now, you start talking about ratings for TV/Movies in America and well you've opened a large can o worms there.
PG-13 Parents Strongly Cautioned. Some material may be inappropriate for children under 13
http://www.mpaa.org/movieratings
Who are the people who rate these movies and what guidlines do they follow, and do you really want to follow the same thing?
These are the questions i would ask myself, and I dont think I would actually.